The system function JavaLib.invoke invokes a method on a native Java™ object or class and may return a value. JavaLib.invoke is one of several Java access functions.
JavaLib.invoke( identifierOrClass javaObjIdOrClass in, method STRING in {, argument anyEglPrimitive in}) returns (result anyJavaPrimitive)
If the native Java method returns a value, the result field is optional.
The following cases apply:
For details on mismatched lengths, see Assignments.
This argument is either a string literal or an variable of type CHAR, DBCHAR, MBCHAR, STRING, 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.
This argument is either a string literal or an variable of type CHAR, DBCHAR, MBCHAR, STRING, or UNICODE. Single- and double-byte blanks are stripped from the beginning and end of the string, which is case sensitive.
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 variable for a Java double, and an EGL smallfloat variable 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.
// call the constructor of the Java Date class and // assign the new object to the identifier "date". JavaLib.storeNew( (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 = JavaLib.invoke( (objId)"date", "toString" ); // assign the standard output stream of the // Java System class to the identifier "systemOut". JavaLib.storeField( (objId)"systemOut", "java.lang.System", "out" ); // call the println method of the output // stream and print today's date. JavaLib.invoke( (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 JavaLib.invoke 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 variable |
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
Related tasks
Syntax diagram for EGL statements and commands