Data encoding

The JVM can use a different code page from CICS® for character encoding; CICS must always use an EBCDIC code page, but the JVM can use another encoding such as ASCII. When you are developing an application that uses the JCICS API, you must ensure that you use the correct encoding.

The JCICS API uses the code page that is specified in the CICS region and not the underlying JVM. So if the JVM uses a different file encoding, your application must handle different code pages. To help you determine which code page CICS is using, CICS provides several Java™ properties:

  • The com.ibm.cics.jvmserver.supplied.ccsid property returns the code page that is specified for the CICS region. By default, the JCICS API uses this code page for its character encoding. However, this value can be overridden in the JVM server configuration.
  • The com.ibm.cics.jvmserver.override.ccsid property returns the value of an override in the JVM profile. The value is a code page that the JCICS API uses for its character encoding, instead of the code page that is used by the CICS region.
  • The com.ibm.cics.jvmserver.local.ccsid property returns the code page that the JCICS API is using for character encoding in the JVM server.

You cannot set any of these properties in your Java application to change the encoding for JCICS. To change the code page, you must ask a system administrator to update the JVM profile to add the JVM system property -Dcom.ibm.cics.jvmserver.override.ccsid.

Encoding example

Any JCICS methods that accept java.lang.String parameters as input are automatically encoded with the correct code page before the data passes to CICS . Similarly, any java.lang.String values that are returned from the JCICS API are encoded in the correct code page. The JCICS API provides helper methods in most classes; these helper methods work with strings and data to determine and set the code page on behalf of the application.

If your application uses the String.getBytes() or new String(byte[] bytes) methods, the application must ensure it uses the correct encoding. If you want to use these methods in your application, you can use the Java property to encode the data correctly: 

String.getBytes(System.getProperty("com.ibm.cics.jvmserver.local.ccsid"))
String(bytes, System.getProperty("com.ibm.cics.jvmserver.local.ccsid"))

The following example shows how to use the JCICS encoding when the application reads a field from a COMMAREA: 

public static void main(CommAreaHolder ca)
{
    //Convert first 8 bytes of ca into a String using JCICS encoding
    String str=new String(ca.getValue(), 0, 8, System.getProperty("com.ibm.cics.jvmserver.local.ccsid"));
}