sysLib.java

The system function sysLib.java invokes a method on a native Java object or class and may return a value. sysLib.java is one of several Java access functions.

sysLib.Java syntax diagram

returnItem

The return item, if present, receives a value from the native Java method.

If the native Java method returns a value, the return item is optional.

The following cases apply:

If the received value is a BigDecimal, BigInteger, byte, short, int, long, float, or double, the return item must be a numeric data type. The characteristics do not need to match the value; for example, a float may be stored in a return item that is declared with no decimal digits. For details on handling overflow, see sysVar.handleOverflow and sysVar.overflowIndicator.
If the received value is a boolean, the return item must be of a numeric primitive type. The value is 1 for true, 0 for false.
If the received value is a byte array, the return item must be of type HEX. For details on mismatched lengths, see Assignments.
If the received value is a String or char, the return item must be of type CHAR, DBCHAR, MBCHAR, or UNICODE--
- If the item is of type MBCHAR or UNICODE the received value is always appropriate
- If the item is of type CHAR, problems can arise if the received value includes characters that correspond to DBCHAR characters
- If the item is of type DBCHAR, problems can arise if the received value includes Unicode characters that correspond to single-byte characters
For details on mismatched lengths, see Assignments.
If the native Java method does not return a value or returns a null, the following cases apply:
- No error occurs in the absence of a return item
- An error occurs at run time if a return item is present; the error is 00001004, as listed later

identifierOrClass

This argument is one of the following entities:

An identifier that refers to an object in the object space; or
The fully qualified name of a Java class.

This argument is either a string literal or an item of type CHAR, DBCHAR, MBCHAR, or UNICODE. If you are specifying an identifier of an object, the identifier must be cast to objID, as in a later example. EGL strips single- and double-byte blanks from the beginning and end of the argument value, which is case sensitive.

Your code cannot invoke a method on an object until you have created an identifier for the object. A later example illustrates this point with java.lang.System.out, which refers to a PrintStream object.

method

The name of the method to call.

This argument is either a string literal or an item of type CHAR, DBCHAR, MBCHAR, or UNICODE. Single- and double-byte blanks are stripped from the beginning and end of the string, which is case sensitive.

argument

A value passed to the method.

A cast may be required, as specified in Java access (system words).

The Java type-conversion rules are in effect. No error occurs, for example, if you pass a short to a method parameter that is declared as an int.

To avoid losing precision, use an EGL float item for a Java double, and an EGL smallfloat item for a Java float. Using one of the other EGL types will probably result in a value being rounded.

The memory area in the invoking program does not change regardless of what the method does.

In the following example, the cast (objId) is required except as noted:

  // call the constructor of the Java Date class and
  // assign the new object to the identifier "date".
  sysLib.JavaStoreNew( (objId)"date", "java.util.Date");

  // call the toString method of the new Date object
  // and assign the output (today's date) to the chaItem.
  // In the absence of the cast (objId), "date" 
  // refers to a class rather than an object.
  chaItem = sysLib.Java( (objId)"date", "toString" );

  // assign the standard output stream of the 
  // Java System class to the identifier "systemOut".
  sysLib.JavaStoreField( (objId)"systemOut", "java.lang.System", "out" );

  // call the println method of the output 
  // stream and print today's date.
  sysLib.Java( (objID)"systemOut", "println", chaItem );

  // The use of "java.lang.System.out" as the first 
  // argument in the previous line would not have been
  // valid, as the argument must either be a 
  // an identifier already in the object space or a class
  // name. The argument cannot refer to a static field.

An error during processing of sysLib.java can set sysVar.errorCode to a value listed in the next table.

Value in sysVar.errorCode	Description
00001000	An exception was thrown by an invoked method or as a result of a class initialization
00001001	The object was null, or the specified identifier was not in the object space
00001002	A public method, field, or class with the specified name does not exist or cannot be loaded
00001003	The EGL primitive type does not match the type expected in Java
00001004	The method returned null, the method does not return a value, or the value of a field was null
00001005	The returned value does not match the type of the return item
00001006	The class of an argument cast to null could not be loaded
00001007	A SecurityException or IllegalAccessException was thrown during an attempt to get information about a method or field; or an attempt was made to set the value of a field that was declared final
00001009	An identifier rather than a class name must be specified; the method or field is not static

Related concepts
Java access functions

Related tasks
Syntax diagram