The Oracle Java Database Connectivity (JDBC) drivers provide globalization support, formerly known as National Language Support (NLS). Globalization support enables you to retrieve data or insert data into a database in any character set that Oracle supports. If the clients and the server use different character sets, then the driver provides the support to perform the conversions between the database character set and the client character set.
This chapter contains the following sections:
Starting from Oracle Database 10g, the
NLS_LANGvariable is no longer part of the JDBC globalization mechanism. The JDBC driver does not check NLS environment. So, setting it has no effect.
The JDBC server-side internal driver provides complete globalization support and does not require any globalization extension files.
JDBC 4.0 includes methods for reading and writing national character set values. You should use these methods when using JSE 6 or later.
19.1 About Providing Globalization Support
The basic Java Archive (JAR) file
ojdbc7.jar, contains all the necessary classes to provide complete globalization support for:
Oracle character sets for
CLOBdata that is not being retrieved or inserted as a data member of an Oracle object or collection type.
VARCHARdata members of object and collection for the character sets
To use any other character sets in
VARCHAR data members of objects or collections, you must include
orai18n.jar in the
CLASSPATH environment variable:
Previous releases depended on the
nls_charset12.zip file. This file is now obsolete.
java -jar orai18n.jar -custom-charsets-jar [jar/zip_filename] -charset characterset_name [characterset_name ...]
For example, if you want to create a custom character set file,
custom_orai18n_ja.jar, that includes the JA16SJIS and JA16EUC character sets, then issue the following command:
$ java -jar orai18n.jar -custom-charsets-jar custom_orai18n_ja.jar -charset JA16SJIS JA16EUC
The output of the command is as follows:
Added Character set : JA16SJIS Added Character set : JA16EUC
If you do not specify a file name for your custom JAR/ZIP file, then a file with the name
jdbc_orai18n_cs.jar is created in the current working directory. Also, for your custom JAR/ZIP file, you cannot specify a name that starts with
If any invalid or unsupported character set name is specified in the command, then no output JAR/ZIP file will be created. If the custom JAR/ZIP file exists, then the file will not be updated or removed.
The custom character set JAR/ZIP does not accept any command. However, it prints the version information and the command that was used to generate the JAR/ZIP file. For example, you have
jdbc_orai18n_cs.zip, the command that displays the information and the displayed information is as follows:
$ java -jar jdbc_orai18n_cs.jar Oracle Globalization Development Kit - 12.1.X.X.X Release This custom character set jar/zip file was created with the following command: java -jar orai18n.jar -custom-charsets-jar jdbc_orai18n_cs.jar -charset WE8ISO8859P15
The limitation to the number of character sets that can be specified depends on that of the shell or command prompt of the operating system. It is certified that all supported character sets can be specified with the command.
If you are using a custom character set, then you need to perform the following so that JDBC supports the custom character set:
After creating the
.nlbfiles as part of the process of creating a custom character set, create
.glbfiles for the newly created character set and also for the
lx0boot.nltfile using the following command:
java -classpath $ORACLE_HOME/jlib/orai18n.jar:$ORACLE_HOME/lib/xmlparserv2.jar Ginstall -[add | a] <NLT_file_name>
Add the generated files and
classpathenvironment variable while executing the JDBC code that connects to the database with the custom character set.
19.2 NCHAR, NVARCHAR2, NCLOB and the defaultNChar Property
By default, the
oracle.jdbc.OraclePreparedStatement interface treats the data type of all the columns in the same way as they are encoded in the database character set. However, since Oracle Database 10g, if you set the value of
oracle.jdbc.defaultNChar system property to
true, then JDBC treats all character columns as being national-language.
The default value of
defaultNChar is false. If the value of
defaultNChar is false, then you must call the
setFormOfUse(<column_Index>, OraclePreparedStatement.FORM_NCHAR) method for those columns that specifically need national-language characters. For example:
PreparedStatement pstmt = conn.prepareStatement("insert into TEST values(?,?,?)"); pstmt.setFormOfUse(1, OraclePreparedStatement.FORM_NCHAR); pstmt.setString(1, myUnicodeString1); // NCHAR column pstmt.setFormOfUse(2, OraclePreparedeStatement.FORM_NCHAR); pstmt.setString(2, myUnicodeString2); // NVARCHAR2 column
If you want to set the value of
true, then specify the following at the command-line:
java -Doracle.jdbc.defaultNChar=true myApplication
If you prefer, then you can also specify
defaultNChar as a connection property and access
Properties props = new Properties(); props.put(OracleConnection.CONNECTION_PROPERTY_DEFAULTNCHAR, "true"); // set URL, username, password, and so on. ... Connection conn = DriverManager.getConnection(props);
If the value of
true, then you should call the
setFormOfUse(<column_Index>, FORM_CHAR) for columns that do not need national-language characters. For example:
PreparedStatement pstmt = conn.prepareStatement("insert into TEST values(?,?,?)"); pstmt.setFormOfUse(3, OraclePreparedStatement.FORM_CHAR); pstmt.setString(3, myString); // CHAR column
If you set the value of
true and then access
CHAR columns, then the database will implicitly convert all
CHAR data into
NCHAR. This conversion has a substantial performance impact.
java.lang.Stringfor character data instead of
CHARis provided only for backward compatibility.
You can also use the
setObjectmethod to access national character set types, but if the
setObjectmethod is used, then the target data type must be specified as
In Oracle Database, SQL strings are converted to the database character set. Therefore you need to keep in mind the following:
In Oracle Database 10g release 1 (10.1) and earlier releases, JDBC drivers do not support any
NCHARliteral (n'...') containing Unicode characters that are not representable in the database character set. All Unicode characters that are not representable in the database character set get corrupted.
If an Oracle Database 10g release 2 (10.2) JDBC driver is connected to an Oracle Database 10g release 2 (10.2) database server, then all
NCHARliterals (n'...') are converted to Unicode literals (u'...') and all non-ASCII characters are converted to their corresponding Unicode escape sequence. This is done automatically to prevent data corruption.
If an Oracle Database 10g release 2 (10.2) JDBC driver is connected to an Oracle Database 10g release 1 (10.1) or earlier database server, then
NCHARliterals (n'...') are not converted and any character that is not representable in the database character set gets corrupted.
19.3 New Methods for National Character Set Type Data in JDK 6
JDBC 4.0 introduces support for the following four additional SQL types to access the national character set types:
These types are similar to the
CLOB types, except that the values are encoded using the national character set. The JDBC specification uses the
String class to represent
LONGNVARCHAR data, and the
NClob class to represent
To retrieve a national character value, an application calls one of the following methods:
getClob method may be used to return an
NClob object since
To specify a value for a parameter marker of national character type, an application calls one of the following methods:
You can use the
setFormOfUse method to specify a national character value in JDK 6. But this practice is discouraged because this method will be deprecated in future release. So, Oracle recommends you to use the methods discussed in this section.
setObject method is used, then the target data type must be specified as