Oracle® Database SQLJ Developer's Guide and Reference 10g Release 2 (10.2) Part Number B16018-02 |
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This chapter discusses internal operations and functionality of the Oracle SQLJ translator and run time.
The following topics are covered:
The following topics summarize the operations executed by the SQLJ translator during a translation:
In this first phase of SQLJ translation, a SQLJ parser and a Java parser are used to process all the source code and check syntax. As the SQLJ translator parses the .sqlj
file, it invokes a Java parser to check the syntax of Java statements and a SQLJ parser to check the syntax of SQLJ constructs (anything preceded by #sql
). The SQLJ parser also invokes the Java parser to check the syntax of Java host variables and expressions within SQLJ executable statements.
The SQLJ parser checks the grammar of SQLJ constructs according to the SQLJ language specification. However, it does not check the grammar of the embedded SQL operations. SQL syntax is not checked until the semantics-checking or offline parsing step.
This syntax-check will look for errors like missing semi-colons, mismatched curly braces, and obvious type mismatches, such as multiplying a number by a string. If the parsers find any syntax errors or type mismatches during this phase, then the translation is aborted and the errors are reported to the user.
Once the SQLJ and Java application source code is verified as syntactically correct, the translator enters into the semantics-checking phase and invokes a SQL semantics-checker or a SQL offline parser or both, according to SQLJ option settings.
Setting the -user
option enables online checking, and setting the -password
and -url
options specifies the database connection, if the password and URL were not specified in the -user
option. The -offline
or -online
option specifies which checker to use. The default, typically sufficient, is a checker front end called OracleChecker
that chooses the most appropriate checker, according to whether you have enabled online checking and which Java Database Connectivity (JDBC) driver you are using.
The -parse
option, true
by default, is for enabling the offline parser, which offers a way to verify SQL and PL/SQL syntax (but not data types against database columns) without necessitating a database connection during translation. Note that some settings of the -parse
option will override the -user
option and disable online checking.
Note:
For ISO code generation, semantics-checking can also be performed on a profile that was produced during a previous execution of the SQLJ translator. Refer to "SQLCheckerCustomizer for Profile Semantics-Checking".The following tasks are always performed during semantics-checking, regardless of the status of online checking or offline parsing:
SQLJ analyzes the types of Java expressions in your SQLJ executable statements.
This includes examining the SQLJ source files being translated, any .java
files entered on the command line, and any imported Java classes whose .class
files or .java
files can be found through the classpath. SQLJ examines whether and how stream types are used in SELECT
or CAST
statements, what Java types are used in iterator columns or INTO
-lists, what Java types are used as input host variables, and what Java types are used as output host variables.
SQLJ also processes FETCH
, CAST
, CALL
, SET TRANSACTION
, VALUES
, and SET
statements syntactically.
Any Java expression in a SQLJ executable statement must have a Java type valid for the given situation and usage. For example, consider the following statement:
#sql [myCtx] { UPDATE ... };
The myCtx
variable, which might be used to specify a connection context instance or execution context instance for this statement, must actually resolve to a SQLJ connection context type or execution context type.
Now consider the following example:
#sql { UPDATE emp SET sal = :newSal };
If newSal
is a variable, as opposed to a field, then an error is generated if newSal
was not previously declared. In any case, an error is generated if it cannot be assigned to a valid Java type or its Java type cannot be used in a SQL statement (for example, java.util.Vector
).
Note:
Semantics-checking of Java types is performed only for Java expressions within SQLJ executable statements. Such errors in your standard Java statements will not be detected until compilation by the Java compiler.SQLJ tries to categorize your embedded SQL operations. Each operation must have a recognizable keyword, such as SELECT
or INSERT
, so that SQLJ knows what kind of operation it is. For example, the following statement will generate an error:
#sql { foo };
If either online checking or offline parsing (or both) is enabled, then SQLJ analyzes and verifies the syntax of embedded SQL and PL/SQL operations.
If either online checking or offline parsing (or both) is enabled, then SQLJ checks the types of Java expressions in SQLJ executable statements against SQL types of corresponding columns in the database and SQL types of corresponding arguments and return variables of stored procedures and functions.
In the process of doing this, SQLJ verifies that the SQL entities used in your SQLJ executable statements, such as tables, views, and stored procedures, actually exist in the database. SQLJ also checks nullability of database columns whose data is being selected into iterator columns of Java primitive types, which cannot process null data. However, nullability is not checked for stored procedure and function output parameters and return values.
For the .sqlj
application source file, the SQLJ translator generates a .java
file and, for ISO standard SQLJ code generation, at least one profile (either in .ser
or .class
files). The .java
contains your translated application source code, class definitions for any private iterators and connection contexts you declared, and, for ISO code, a profile-keys class definition generated and used internally by SQLJ.
Note:
No profiles or profile-keys class are generated if you use the default Oracle-specific code generation mode.With ISO code generation, there are no profiles or profile-keys class if you do not use any SQLJ executable statements in your code.
Generated Application Code in .java File
For the default Oracle-specific code generation, the generated .java
file for your application contains direct calls to the Oracle JDBC driver in place of the original SQLJ executable statements. There are also calls to an Oracle-specific SQLJ run time. For ISO standard SQLJ code generation, SQLJ executable statements are replaced by calls to the SQLJ run time, which in turn contains calls to the JDBC driver.
For convenience, generated .java
files also include a comment for each of your #sql
statements, repeating the statement in its entirety for reference. The generated .java
file will have the same base name as the input .sqlj
file, which would be the name of the public class defined in the .sqlj
file or the first class defined if there are no public classes. For example, Foo.sqlj
defines the Foo
class. The Foo.java
source file will be generated by the translator.
The location of the generated .java
file depends on whether and how you set the SQLJ -dir
option. By default, the .java
file will be placed in the directory of the .sqlj
input file.
Generated Profile-Keys Class in .java File (ISO Code Generation)
If you use ISO standard SQLJ code generation, SQLJ generates a profile-keys class that it uses internally during run time to load and access the serialized profile. This class contains mapping information between the SQLJ run time calls in your translated application and the SQL operations placed in the serialized profile. It also contains methods to access the serialized profile.
Note:
If you use the default Oracle-specific code generation, no profiles or profile-keys classes are generated.The profile-keys class is defined in the same .java
output file that has your translated application source code, with a class name based on the base name of your .sqlj
source file as follows:
Basename_SJProfileKeys
For example, translating Foo.sqlj
defines the following profile-keys class in the generated .java
file:
Foo_SJProfileKeys
If your application is in a package, this is reflected appropriately. For example, translating Foo.sqlj
in the a.b
package defines the following class:
a.b.Foo_SJProfileKeys
Generated Profiles in .ser or .class Files (ISO Code Generation)
If you use ISO standard SQLJ code generation, SQLJ generates profiles that it uses to store information about the SQL operations found in the input file. A profile is generated for each connection context class that you use in your application. It describes the operations to be performed using instances of the associated connection context class, such as SQL operations to execute, tables to access, and stored procedures and functions to call.
Note:
If you use the default Oracle-specific code generation, then information about the SQL operations is embedded in the generated code, which calls the Oracle JDBC driver directly. In this case, SQLJ does not generate profiles.Profiles are generated in .ser
serialized resource files. However, if you enable the SQLJ -ser2class
option, then the profiles are automatically converted to .class
files as part of the translation. In this case, no further customization of the profile is possible. You would have to delete the .class
file and rerun the SQLJ translator to regenerate the profile.
Profile base names are generated similarly to the profile-keys class name. They are fully qualified with the package name, followed by the .sqlj
file base name, followed by the string:
_SJProfilen
Where n
is a unique number, starting with 0, for each profile generated for a particular .sqlj
input file.
Again using the example of the Foo.sqlj
input file, if two profiles are generated, then they will have the following base names (presuming no package):
Foo_SJProfile0 Foo_SJProfile1
If Foo.sqlj
is in the a.b
package, then the profile base names will be:
a.b.Foo_SJProfile0 a.b.Foo_SJProfile1
Physically, a profile exists as a Java serialized object contained within a resource file. Resource files containing profiles use the .ser
extension and are named according to the base name of the profile (excluding package names). Resource files for the two previously mentioned profiles will be named as follows:
Foo_SJProfile0.ser Foo_SJProfile1.ser
Or, they will be named Foo_SJProfile0.class
and Foo_SJProfile1.class
if you enable the -ser2class
option. If you choose this option, then the conversion to .class
takes place after the customization step.
The location of these files depends on how the SQLJ -d
option is set, which determines where all generated .ser
and .class
files are placed.
More About Generated Calls to SQLJ Run Time
When #sql
statements are replaced by calls to the JDBC driver (for Oracle-specific code generation) or to the SQLJ run time (for ISO standard SQLJ code generation), these calls implement the steps in Table 9-1.
Table 9-1 Steps for Generated Calls, ISO Standard Versus Oracle-Specific
Steps for ISO Standard Code Generation | Steps for Oracle Code Generation |
---|---|
Get a SQLJ statement object, using information stored in the associated profile entry. |
Get an Oracle JDBC statement object. |
Bind inputs into the statement, using |
Bind inputs using Oracle JDBC statement methods and, if necessary, register output parameters. |
Execute the statement, using the |
Execute the Oracle statement. |
Create iterator instances, if applicable. |
Create iterator instances, if applicable. |
Retrieve outputs from the statement, using |
Retrieve outputs from the statement using appropriate JDBC getter methods. |
Close the SQLJ statement object (by default, recycling it through the SQLJ statement cache). |
Close the JDBC statement object (by default, recycling it through the JDBC statement cache). |
A SQLJ run time uses SQLJ statement objects that are similar to JDBC statement objects, although a particular implementation of SQLJ might or might not use JDBC statement classes directly. SQLJ statement classes add functionality particular to SQLJ. For example:
Standard SQLJ statement objects raise a SQL exception if a null value from the database is to be output to a primitive Java type, such as int
or float
, which cannot take null values.
Oracle SQLJ statement objects allow user-defined object and collection types to be passed to or retrieved from an Oracle database.
After code generation, SQLJ invokes the Java compiler to compile the generated .java
file. This produces a .class
file for each class you defined in your application, including iterator and connection context declarations, as well as a .class
file for the generated profile-keys class if you use ISO code generation (and presuming your application uses SQLJ executable statements). Any .java
files you specified directly on the SQLJ command line (for type-resolution, for example) are compiled at this time as well.
In the example used in "Code Generation", the following .class
files would be produced in the appropriate directory (given package information in the source code):
Foo.class
Foo_SJProfileKeys.class
(ISO code generation only)
A .class
file for each additional class you defined in Foo.sqlj
A .class
file for each iterator and connection context class you declared in Foo.sqlj
(whether public or private)
To ensure that .class
files and profiles (if any, whether .ser
or .class
) will be located in the same directory, SQLJ passes its -d
option to the Java compiler. If the -d
option is not set, then .class
files and profiles are placed in the same directory as the generated .java
file, which is placed according to the -dir
option setting.
In addition, so that SQLJ and the Java compiler will use the same encoding, SQLJ passes its -encoding
option to the Java compiler unless the SQLJ -compiler-encoding-flag
is turned off. If the -encoding
option is not set, then SQLJ and the compiler will use the setting in the Java virtual machine (JVM) file.encoding
property.
By default, SQLJ invokes the standard javac
compiler of the Sun Microsystems Java Development Kit (JDK), but other compilers can be used instead. You can request that an alternative Java compiler be used by setting the SQLJ -compiler-executable
option.
Note:
If you are using the SQLJ-encoding
option but using a compiler that does not have an -encoding
option, then turn off the SQLJ -compiler-encoding-flag
. Otherwise, SQLJ will attempt to pass the -encoding
option to the compiler.For information about SQLJ support for compiler options and compiler-related SQLJ options, refer to the following:
After Java compilation, if you are using ISO standard code generation, then the generated profiles containing information about your embedded SQL instructions are customized, so that your application can work efficiently with your database and use vendor-specific extensions.
Note:
If you use the default Oracle-specific code generation, then SQLJ produces no profiles and skips the customization step. Your code will support Oracle-specific features through direct calls to Oracle JDBC application programming interfaces (APIs).To accomplish customization, SQLJ invokes a front end called the customizer harness, which is a Java class that functions as a command-line utility. The harness, in turn, invokes a particular customizer, either the default Oracle customizer or a customizer that you specify through SQLJ option settings.
During customization, profiles are updated in the following ways:
To allow your application to use any vendor-specific database types or features, if applicable
To tailor the profiles so that your application is as efficient as possible in using features of the relevant database environment
Without customization, you can access and use only standard JDBC types.
For example, the Oracle customizer can update a profile to support a SQL PERSON
type that you had defined. You could then use PERSON
as you would any other supported data type.
You must also customize with the Oracle customizer to use any of the oracle.sql
type extensions.
Note:
Be aware of the following regarding profile customization:The Oracle SQLJ run time and an Oracle JDBC driver will be required by your application whenever you use the Oracle customizer during translation, even if you do not use Oracle extensions in your code.
The generic SQLJ run time will be used if your application has no customizations, or none suitable for the connection.
You can customize previously created profiles by specifying .ser
files, or .jar
files containing .ser
files, on the command line. But you cannot do this in the same running of SQLJ where translations are taking place. You can specify .ser
/.jar
files to be customized or .sqlj
/.java
files to be translated, compiled, and customized, but not both categories. For more information about how .jar
files are used, refer to "JAR Files for Profiles".
For more information about profile customization, refer to Appendix A, "Customization and Specialized Customizers".
Also see the following for information about SQLJ options related to profile customization:
This section provides an overview of SQLJ translator messages and exit codes. It covers the following topics:
There are three major levels of SQLJ messages that you may encounter during the translation phase: error, warning, and information. Warning messages can be further broken down into two levels: non-suppressible and suppressible. Therefore, there are four message categories (in order of seriousness):
Errors
Non-suppressible warnings
Suppressible warnings
Information
You can control suppressible warnings and information by using the SQLJ -warn
option.
Error messages, prefixed by Error:
, indicate that one of the following has been encountered:
A condition that would prevent compilation (for example, the source file contains a public class whose name does not match the base file name)
A condition that would result in a run-time error if the code were executed (for example, the code attempts to fetch a VARCHAR
into a java.util.Vector
, using an Oracle JDBC driver)
If errors are encountered during SQLJ translation, then no output is produced and compilation and customization are not executed.
Non-suppressible warning messages, prefixed by Warning:
, indicate that one of the following has been encountered:
A condition that would probably, but not necessarily, result in a run-time error if the code were executed (for example, a SELECT
statement whose output is not assigned to anything)
A condition that compromises the ability of SQLJ to verify run-time aspects of your source code (for example, not being able to connect to the database you specify for online checking)
A condition that presumably resulted from a coding error or oversight
SQLJ translation will complete if a non-suppressible warning is encountered, but you should analyze the problem and determine if it should be fixed before running the application. If online checking is specified but cannot be completed, then offline checking is performed instead.
Note:
For logistical reasons, the parser that the SQLJ translator uses to analyze SQL operations is not the same top-level SQL parser that will be used at run time. Therefore, errors might occasionally be detected during translation that will not actually cause problems when your application runs. Accordingly, such errors are reported as non-suppressible warnings, rather than fatal errors.Suppressible warning messages, also prefixed by Warning:
, indicate that there is a problem with a particular aspect of your application, such as portability. An example of this is using an Oracle-specific type, such as oracle.sql.NUMBER
, to read from or write to Oracle Database 11g.
Informational or status messages prefixed by Info:
do not indicate an error condition. They merely provide additional information about what occurred during the translation phase.
Suppressible warning and status messages can be suppressed by using the various -warn
option flags:
cast/nocast
: The nocast
setting suppresses warnings about possible run-time errors when trying to cast an object type instance to an instance of a subtype.
precision/noprecision
: The noprecision
setting suppresses warnings regarding possible loss of data precision during conversion.
nulls/nonulls
: The nonulls
setting suppresses warnings about possible run-time errors due to nullable columns or types.
portable/noportable
: The noportable
setting suppresses warnings regarding SQLJ code that uses Oracle-specific features or might otherwise be non-standard and, therefore, not portable to other environments.
strict/nostrict
: The nostrict
setting suppresses warnings issued if there are fewer columns in a named iterator than in the selected data that is to populate the iterator.
verbose/noverbose
: The noverbose
setting suppresses status messages that are merely informational and do not indicate error or warning conditions.
See Also:
"Translator Warnings (-warn)"If you receive warnings during your SQLJ translation, then you can try running the translator again with -warn=none
to see if any of the warnings are of the more serious (non-suppressible) variety.
Table 9-2 summarizes the categories of error and status messages generated by the SQLJ translator.
Table 9-2 SQLJ Translator Error Message Categories
Message Category | Prefix | Indicates | Suppressed By |
---|---|---|---|
Error |
|
Fatal error that will cause compilation failure or run-time failure (translation aborted) |
NA |
Non-suppressible warning |
|
Condition that prevents proper translation or might cause run-time failure (translation completed) |
NA |
Suppressible warning |
|
Problem regarding a particular aspect of your application (translation completed) |
|
Informational/status message |
|
Information regarding the translation process |
|
In addition to the error, warning, and information messages, SQLJ can produce status messages throughout all phases of SQLJ operation: translation, compilation, and customization. Status messages are produced as each file is processed and at each phase of SQLJ operation.
You can control status messages by using the SQLJ -status
option.
See Also:
"Real-Time Status Messages (-status)"The following exit codes are returned by the SQLJ translator to the operating system upon completion:
0
: No error in execution
1
: Error in SQLJ execution
2
: Error in Java compilation
3
: Error in profile customization
4
: Error in class instrumentation, the optional mapping of line numbers from your .sqlj
source file to the resulting .class
file
5
: Error in ser2class
conversion, the optional conversion of profile files from .ser
files to .class
files
Notes:
If you issue the -help
or -version
option, then the SQLJ exit code is 0
.
If you run SQLJ without specifying any files to process, then SQLJ issues help output and returns exit code 1
.
This section presents information about the Oracle SQLJ run time, which is a thin layer of pure Java code that runs above the JDBC driver.
If you use the default Oracle-specific code generation, then the SQLJ run time layer becomes even thinner, with a run time subset being used in conjunction with an Oracle JDBC driver. Most of the run time functionality is compiled directly into Oracle JDBC calls. You cannot use a non-Oracle JDBC driver.
When SQLJ translates SQLJ source code using ISO standard code generation, embedded SQL commands in your Java application are replaced by calls to the SQLJ run time. Run time classes act as wrappers for equivalent JDBC classes, providing special SQLJ functionality. When the end user runs the application, the SQLJ run time acts as an intermediary, reading information about your SQL operations from your profile and passing instructions along to the JDBC driver.
Generally speaking, however, a SQLJ run time can be implemented to use any JDBC driver or vendor-proprietary means of accessing the database. The Oracle SQLJ run time requires a JDBC driver, but can use any standard JDBC driver. To use Oracle-specific data types and features, however, you must use an Oracle JDBC driver. For the purposes of this document, it is generally assumed that you are using an Oracle database and one of the Oracle JDBC drivers.
Note:
For ISO standard SQLJ code generation, the Oracle SQLJ run time and an Oracle JDBC driver will be required by your application whenever you use the Oracle customizer during translation, even if you do not use Oracle extensions in your code. The generic SQLJ run time will be used if your application has no customizations, or none suitable for the connection.The Oracle SQLJ run time includes packages you will likely import and use directly, and others that are used only indirectly.
Note:
These packages are included in the run time librariesruntime12
, runtime12ee
, and runtime
.Packages Used Directly
The packages containing classes that you can import and use directly in your application are:
sqlj.runtime
This package includes the ExecutionContext
class, ConnectionContext
interface, ConnectionContextFactory
interface, ResultSetIterator
interface, ScrollableResultSetIterator
interface, and wrapper classes for streams (BinaryStream
and CharacterStream
, as well as the deprecated AsciiStream
and UnicodeStream
).
Interfaces and abstract classes in this package are implemented by classes in the sqlj.runtime.ref
or oracle.sqlj.runtime
package or by classes generated by the SQLJ translator.
sqlj.runtime.ref
The classes in this package implement interfaces and abstract classes in the sqlj.runtime
package. You will likely use the sqlj.runtime.ref.DefaultContext
class, which is used to specify your default connection and create default connection context instances. The other classes in this package are used internally by SQLJ in defining classes during code generation, such as iterator classes and connection context classes that you declare in your SQLJ code.
oracle.sqlj.runtime
This package contains the Oracle
class that you can use to instantiate the DefaultContext
class and establish your default connection. It also contains Oracle-specific run time classes used by the Oracle implementation of SQLJ, including functionality to convert to and from Oracle type extensions.
Note:
Packages whose names begin withoracle
are for Oracle-specific SQLJ features.Packages Used Indirectly
The packages containing classes that are for internal use by SQLJ are:
sqlj.runtime.profile
This package contains interfaces and abstract classes that define what SQLJ profiles look like (applicable only for ISO standard code generation). This includes the EntryInfo
and TypeInfo
classes. Each entry in a profile is described by an EntryInfo
object, where a profile entry corresponds to a SQL operation in your application. Each parameter in a profile entry is described by a TypeInfo
object.
The interfaces and classes in this package are implemented by classes in the sqlj.runtime.profile.ref
package.
sqlj.runtime.profile.ref
This package contains classes that implement the interfaces and abstract classes of the sqlj.runtime.profile
package and are used internally by the SQLJ translator in defining profiles (for ISO standard code generation only). It also provides the default JDBC-based run time implementation.
sqlj.runtime.error
This package, used internally by SQLJ, contains resource files for all generic (not Oracle-specific) error messages that can be generated by the SQLJ translator.
oracle.sqlj.runtime.error
This package, used internally by SQLJ, contains resource files for all Oracle-specific error messages that can be generated by the SQLJ translator.
Run-time errors can be generated by any of the following:
SQLJ run time
JDBC driver
RDBMS
In any of these cases, a SQL exception is generated as an instance of the java.sql.SQLException
class, or as a subclass, such as sqlj.runtime.SQLNullException
.
Depending on where the error came from, there might be meaningful information you can retrieve from an exception using the getSQLState()
, getErrorCode()
, and getMessage()
methods. SQLJ errors, for example, include meaningful SQL states and messages.
See Also:
"Retrieving SQL States and Error Codes"If errors are generated by the Oracle JDBC driver or RDBMS at run time, look at the prefix and consult the appropriate documentation:
Oracle Database JDBC Developer's Guide and Reference for JDBC errors
Oracle error message documentation for RDBMS errors (see "Related Documents")
The Oracle SQLJ implementation uses the Java built-in capabilities for globalization support. This section discusses the following:
Basics of SQLJ support for globalization and native character encoding, starting with background information covering some of the implementation details of character encoding and language support in the Oracle implementation
Options available through the SQLJ command line that enable you to adjust your Oracle Globalization Support configuration
Extended Oracle globalization support
Relevant manipulation outside of SQLJ for globalization support
Note:
Some prior knowledge of Oracle Globalization Support is assumed, particularly regarding character encoding and locales. For information, refer to the Oracle Database Globalization Support Guide.This section covers the following topics:
There are two main areas of SQLJ globalization support:
Character encoding
There are three parts to this:
Character encoding for reading and generating source files during SQLJ translation
Character encoding for generating error and status messages during SQLJ translation
Character encoding for generating error and status messages when the application runs
Language support
This determines which translations of error and status message lists are used when SQLJ outputs messages to the user, either during SQLJ translation or at SQLJ run time.
Globalization support at run time is transparent to the user, presuming your SQLJ source code and SQL character data use only characters that are within the database character set. SQL character data is transparently mapped into and out of Unicode.
Note that for multi-language applications, it is advisable to use one of the following options:
Use a database whose character set supports Unicode.
Even if your database character set does not support Unicode, specify that the national language character set supports Unicode. (Refer to the Oracle Database Globalization Support Guide.) In this case, you will typically use the SQLJ Unicode character types described in "SQLJ Extended Globalization Support".
Notes:
The SQLJ translator fully supports Unicode 2.0 and Java Unicode escape sequences. However, the SQLJ command-line utility does not support Unicode escape sequences. You can use only native characters supported by the operating system. Command-line options requiring Unicode escape sequences can be entered in a SQLJ properties file instead, because properties files do support Unicode escape sequences.
Encoding and conversion of characters in your embedded SQL operations and characters read or written to the database, are handled by JDBC directly. SQLJ does not play a role in this. If online semantics-checking is enabled during translation, however, then you will be warned if there are characters within the text of your SQL data manipulation language (DML) operations that might not be convertible to the database character set.
For information about JDBC globalization support functionality, refer to the Oracle Database JDBC Developer's Guide and Reference.
Overview of Character Encoding
The character encoding setting for source files tells SQLJ two things:
How source code is represented in .sqlj
and .java
input files that the SQLJ translator must read
How SQLJ should represent source code in .java
output files that it generates
By default, SQLJ uses the encoding indicated by the JVM file.encoding
property. If your source files use other encodings, then you must indicate this to SQLJ so that appropriate conversion can be performed.
Use the SQLJ -encoding
option to accomplish this. SQLJ also passes the -encoding
setting to the compiler for it to use in reading .java
files, unless the SQLJ -compiler-encoding-flag
is off.
Note:
Do not alter thefile.encoding
system property to specify encodings for source files. This might impact other aspects of your Java operation and might offer only a limited number of encodings, depending on platform or operating system considerations.The system character-encoding setting also determines how SQLJ error and status messages are represented when output to the user, either during translation or during run time when the end user is running the application. This is set according to the file.encoding
property and is unaffected by the SQLJ -encoding
option.
For source file encoding, you can use the -encoding
option to specify any character encoding supported by your Java environment. If you are using the Sun Microsystems JDK, then these are listed in the native2ascii
documentation, which you can find at the following Web site:
http://java.sun.com/j2se/1.3/docs/tooldocs/solaris/native2ascii.html
Dozens of encodings are supported by the Sun Microsystems JDK. These include 8859_1
through 8859_9
(ISO Latin-1 through ISO Latin-9), JIS
(Japanese), SJIS
(shift-JIS, Japanese), and UTF8
.
Character Encoding Notes
Be aware of the following:
A character that is not representable in the encoding used, for either messages or source files, can always be represented as a Java Unicode escape sequence. This is of the form \uHHHH
, where each H is a hexadecimal digit.
As a .sqlj
source file is read and processed during translation, error messages quote source locations based on character position (not byte position) in the input encoding.
Encoding settings, either set through the SQLJ -encoding
option or the Java file.encoding
setting, do not apply to Java properties files, such as sqlj.properties
and connect.properties
. Properties files always use the encoding 8859_1
. This is a feature of Java in general, not SQLJ in particular. However, you can use Unicode escape sequences in a properties file. You can use the native2ascii
utility to determine escape sequences.
SQLJ error and status reporting, either during translation or during run time, uses the Java locale setting in the JVM user.language
property. Users typically do not have to alter this setting.
Language support is implemented through message resources that use key/value pairs. For example, where an English-language resource has a key/value pair of "OkKey", "Okay"
, a German-language resource has a key/value pair of "OkKey", "Gut"
. The locale setting determines the message resources used.
SQLJ supports locale settings of en
(English), de
(German), fr
(French), and ja
(Japanese).
Note:
Java locale settings can support country and variant extensions in addition to language extensions. For example, considerErrorMessages_de_CH_var1
, where CH
is the Swiss country extension of German and var1
is an additional variant. SQLJ, however, currently supports only language extensions (de
in this example), ignoring country and variant extensions.The Oracle SQLJ implementation provides syntax that enables you to set the following:
The character encoding used by the SQLJ translator and Java compiler in representing source code
Use the SQLJ -encoding
option.
The character encoding used by the SQLJ translator and run time in representing error and status messages
Use the SQLJ -J
prefix to set the Java file.encoding
property.
The locale used by the SQLJ translator and run time for error and status messages
Use the SQLJ -J
prefix to set the Java user.language
property.
Setting Character Encoding for Source Code
Use the SQLJ -encoding
option to determine the character encoding used in representing .sqlj
files read by the translator, .java
files generated by the translator, and .java
files read by the compiler. The option setting is passed by SQLJ to the compiler, unless the SQLJ -compiler-encoding-flag
is off.
This option can be set on the command line or SQLJ_OPTIONS
environment variable, as in the following example:
-encoding=SJIS
Alternatively, you can set it in a SQLJ properties file, as follows:
sqlj.encoding=SJIS
If the encoding option is not set, then both the translator and compiler will use the encoding specified in the JVM file.encoding
property. This can also be set through the SQLJ command line.
See Also:
"Encoding for Input and Output Source Files (-encoding)" and "Compiler Encoding Support (-compiler-encoding-flag)"Note:
If your-encoding
is to be set routinely to the same value, then it is most convenient to specify it in a properties file, as in the second example.Setting Character Encoding and Locale for SQLJ Messages
Character encoding and locale for SQLJ error and status messages produced, during both translation and run time, are determined by the Java file.encoding
and user.language
properties. Although it is typically not necessary, you can set these and other JVM properties in the SQLJ command line by using the SQLJ -J
prefix. Options marked by this prefix are passed to the JVM.
Set the character encoding as in the following example, which specifies shift-JIS Japanese character encoding:
-J-Dfile.encoding=SJIS
Note:
Only a limited number of encodings might be available, depending on platform or operating system considerations.Set the locale as in the following example (which specifies Japanese locale):
-J-Duser.language=ja
The -J
prefix can be used on the command line or SQLJ_OPTIONS
environment variable only. It cannot be used in a properties file, because properties files are read after the JVM is invoked.
Notes:
If your file.encoding
, user.language
, or any other Java property is to be set routinely to the same value, it is most convenient to specify -J
settings in the SQLJ_OPTIONS
environment variable. This way, you do not have to repeatedly specify them on the command line. The syntax is essentially the same as on the command line. For more information, refer to "SQLJ_OPTIONS Environment Variable for Option Settings".
Remember that if you do not set the SQLJ -encoding
option, then setting file.encoding
will affect encoding for source files as well as error and status messages.
Be aware that altering the file.encoding
property might have unforeseen consequences on other aspects of your Java operations. Also, any new setting must be compatible with your operating system.
See Also:
"Command-Line Syntax and Operations" and "Options to Pass to the Java Virtual Machine (-J)"SQLJ Command-Line Example: Setting Encoding and Locale
Following is a complete SQLJ command line, including JVM file.encoding
and user.language
settings:
% sqlj -encoding=8859_1 -J-Dfile.encoding=SJIS -J-Duser.language=ja Foo.sqlj
This example uses the SQLJ -encoding
option to specify 8859_1
(Latin-1) for source code representation during SQLJ translation. This encoding is used by the translator in reading the .sqlj
input file and in generating the .java
output file. The encoding is then passed to the Java compiler to be used in reading the generated .java
file. The -encoding
option, when specified, is always passed to the Java compiler unless the SQLJ -compiler-encoding-flag
is disabled.
For error and status messages output during translation of Foo.sqlj
, the SQLJ translator uses the SJIS
encoding and the ja
locale.
The Oracle SQLJ implementation includes support for Java types (Unicode character types) derived from existing character and stream types that convey expected usage for globalization. In SQLJ it is not possible to use JDBC statement or result set methods directly that otherwise serve the purpose of globalization support. If you are interested in information about those methods, refer to the Oracle Database JDBC Developer's Guide and Reference
If the database natively supports Unicode, then the types described in "Java Types for Globalization Support" are unnecessary. In this case, globalization support will be handled transparently. It is when the database does not natively support Unicode, but has a national language character set that does support Unicode, that you will typically use these types (for columns that use the national language character set).
Java Types for Globalization Support
The Oracle SQLJ implementation provides a number of Java types for globalization support. Table 9-3 notes the correspondence between these globalization support types and general-use JDBC and SQLJ character and stream types. Each globalization support type, except for NString
, is a subclass of its corresponding JDBC or SQLJ type.
Table 9-3 JDBC and SQLJ Types and Corresponding Globalization Types
In situations where your application must handle national language character strings, either inserting them into or selecting them from national language character set columns, use the globalization support types instead of the corresponding general-use types.
Notes:
All globalization support types add automatic registration of intended usage for IN
and OUT
parameters, but are otherwise identical in usage to the corresponding JDBC or SQLJ type (including constructors).
Use of globalization support types is unnecessary in iterator columns, because the underlying network protocol supports national language characters implicitly for the underlying result sets.
The oracle.sql.CHAR
class, and therefore its NCHAR
subclass, provides only constructors that require explicit knowledge of the database character set. Therefore, the oracle.sql.NString
class, a wrapper for java.lang.String
, is preferable in most circumstances. The NString
class provides simpler constructors and ensures that the national language character form of use is registered with the JDBC driver.
Following are the key NString
methods:
NString(String)
: This constructor creates an NString
instance from an existing String
instance.
String toString()
: This method returns the underlying String
instance.
String getString()
: This method also returns the underlying String
instance.
The toString()
method enables you to use the NString
instance in string concatenation expressions (such as "a"+b
, where b
is a string). The getString()
method, provided in the CHAR
superclass, is supported as well for uniformity. In addition, the member methods of the String
class are carried over to the NString
wrapper class to enable you to write more concise code.
In SQLJ applications, for versions prior to Oracle Database 11g, you must use host variables of the NString
type to bind columns of the NCHAR
type. For example, consider the following table:
CREATE TABLE Tbl1 ( ColA CHAR NColB NCHAR )
To insert a row in this table through a SQLJ application, use a code similar to the following:
... String v_a = "\uFF5E"; NString v_nb = "\uFF5E"; #sql {INSERT INTO Tbl1 (ColA, NColB) VALUES (:v_a, :v_nb)}; ...
In Oracle Database 11g release 1 (11.1), SQLJ applications can use String
variables to bind NCHAR
columns. Therefore, the preceding example can be rewritten as follows:
... String v_a = "\uFF5E"; String v_nb = "\uFF5E"; #sql {INSERT INTO Tbl1 (ColA, NColB) VALUES (:v_a, :v_nb)}; ...
However, if you want to use String
host variable to bind to NCHAR
columns, then you must translate the SQLJ file with the -ncharconv
SQLJ translator option, as follows:
sqlj -ncharconv [-options] app.sqlj
In the preceding command, options
can be other SQLJ options and app.sqlj
is the SQLJ file that contains the code.
When this option is used, the setFormOfUse
method will be generated for all binds to character columns, that is, CHAR
or NCHAR
columns.
Note:
When the SQLJ file is compiled with the-ncharconv
option, the setFormOfUse
method is used in the generated code for codegen=oracle
. For codegen=iso
, this option information is passed to the Oracle SQLJ run time, which internally uses SetFormOfUse
for bind at run time.The SQLJ application can use String
host variable to retrieve data from the server without using the -ncharconv
option, because the information about the column type is fetched at the client side and JDBC internally sets the form for the appropriate columns.
Note:
There may be a small difference in the performance when using the-ncharconv
option, depending on the database character set and national charster set and the number of character columns in the table.See Also:
"NCHAR Bind (-ncharconv)"Globalization Support Examples
The following examples show use of the NString
class:
NString
as IN
argument
This example uses an NString
instance as an input parameter to the database.
import oracle.sql.NString; ... NString nc_name = new NString("Name with strange characters"); #sql { update PEOPLE set city = :(new NString("\ufff2")), name = :nc_name where num= :n }; ...
NString
as OUT
argument
This example uses an NString
instance as an output parameter from the database.
import oracle.sql.NString; ... NString nstr; #sql { call foo(:out nstr) }; System.out.println("Result is: "+nstr); // or, explicitly: System.out.println("Result is: "+nstr.toString()); ...
NString
as Result Set
column
This example uses the NString
type for an iterator column. Such usage is superfluous, given that the underlying network protocol supports national language characters implicitly, but harmless. This example also shows use of one of the String
methods, substring()
, that is carried over to NString
.
import oracle.sql.NString; import oracle.sql.NCLOB; ... #sql iterator NIter(NString title, NCLOB article); NIter nit; #sql nit = { SELECT article, title FROM page_table }; while (nit.next()) { System.out.println("<TITLE>"+nit.title()+"</TITLE>"); ... nit.article().substring(0, 1000); ... }
Note:
Using theNCHAR
type instead of the NString
type for the preceding examples requires the following changes:
Use the appropriate NCHAR
constructor. NCHAR
constructors mirror CHAR
constructors, such as the following:
NCHAR(String str, oracle.sql.CharacterSet charset)
Although you have the option of using either toString()
or getString()
to retrieve the underlying String
instance from an NString
instance, for an NCHAR
instance you must use the getString()
method. When using the NString
type, the toString()
method is used automatically for string concatenation, such as in "NString
as OUT
argument".
This section discusses ways to manipulate your Oracle Globalization Support configuration outside of SQLJ.
Setting Encoding and Locale at Application Run Time
As with any end user running any Java application, those running your SQLJ application can specify JVM properties, such as file.encoding
and user.language
directly, as they invoke the JVM to run your application. This determines the encoding and locale used for message output as your application executes.
They can accomplish this as in the following example:
% java -Dfile.encoding=SJIS -Duser.language=ja Foo
This will use SJIS
encoding and Japanese locale.
Using API to Determine Java Properties
In Java code, you can determine values of Java properties by using the java.lang.System.getProperty()
method, specifying the appropriate property. For example:
public class Settings { public static void main (String[] args) { System.out.println("Encoding: " + System.getProperty("file.encoding") + ", Language: " + System.getProperty("user.language")); } }
You can compile this and run it as a standalone utility.
There is also a getProperties()
method that returns the values of all properties, but this will raise a security exception if you try to use it in code that runs in the server.
Using native2ascii for Source File Encoding
If you are using a Sun Microsystems JDK, then there is an alternative to having SQLJ do the character encoding for your source files. You can use the native2ascii
utility to convert sources with native encoding to sources in 7-bit ASCII with Unicode escape sequences.
Note:
To use SQLJ to translate source created bynative2ascii
, ensure that the JVM that invokes SQLJ has a file.encoding
setting that supports some superset of 7-bit ASCII. This is not the case with settings for EBCDIC or Unicode encoding.Run native2ascii
as follows:
% native2ascii <options> <inputfile> <outputfile>
Standard input or standard output are used if you omit the input file or output file. Two options are supported:
-reverse
(Reverse the conversion. Convert from Latin-1 or Unicode to native encoding)
-encoding <
encoding
>
For example:
% native2ascii -encoding SJIS Foo.sqlj Temp.sqlj
For more information, see the following Web site:
http://java.sun.com/j2se/1.3/docs/tooldocs/solaris/native2ascii.html