Java Doc for ClassBodyEvaluator.java in  » Scripting » jacl » org » codehaus » janino » Java Source Code / Java DocumentationJava Source Code and Java Documentation

Example:

 import java.util.*;
 static private int a = 1;
 private int b = 2;
 public void func(int c, int d) {
 return func2(c, d);
 }
 private static void func2(int e, int f) {
 return e * f;
 }
 

The optionalClassLoader serves two purposes:

• It is used to look for classes referenced by the class body.
• It is used to load the generated Java^TM class into the JVM; directly if it is a subclass of ByteArrayClassLoader , or by creation of a temporary ByteArrayClassLoader if not.

1. Create the ClassBodyEvaluator using ClassBodyEvaluator.ClassBodyEvaluator()
2. Configure the ClassBodyEvaluator by calling any of the following methods:
   • org.codehaus.janino.SimpleCompiler.setParentClassLoader(ClassLoader)
   • ClassBodyEvaluator.setDefaultImports(String[])
3. Call any of the org.codehaus.janino.Cookable.cook(Scanner) methods to scan, parse, compile and load the class body into the JVM.

To compile a class body and immediately instantiate an object, one of the ClassBodyEvaluator.createFastClassBodyEvaluator(Scanner,Class,ClassLoader) methods can be used.

The generated class may optionally extend/implement a given type; the returned instance can safely be type-casted to that optionalBaseType.

Example:

 public interface Foo {
 int bar(int a, int b);
 }
 ...
 Foo f = (Foo) ClassBodyEvaluator.createFastClassBodyEvaluator(
 new Scanner(null, new StringReader("public int bar(int a, int b) { return a + b; }")),
 Foo.class,                  // Base type to extend/implement
 (ClassLoader) null          // Use current thread's context class loader
 );
 System.out.println("1 + 2 = " + f.bar(1, 2));
 

 ClassBodyEvaluator cbe = new ClassBodyEvaluator();
 cbe.cook(classBody);

 ClassBodyEvaluator cbe = new ClassBodyEvaluator();
 cbe.cook(optionalFileName, is);

 ClassBodyEvaluator cbe = new ClassBodyEvaluator();
 cbe.cook(optionalFileName, reader);

 ClassBodyEvaluator cbe = new ClassBodyEvaluator();
 cbe.setParentClassLoader(optionalParentClassLoader);
 cbe.cook(scanner);

 ClassBodyEvaluator cbe = new ClassBodyEvaluator();
 cbe.setExtendedType(optionalExtendedType);
 cbe.setImplementedTypes(implementedTypes);
 cbe.setParentClassLoader(optionalParentClassLoader);
 cbe.cook(scanner);

 ClassBodyEvaluator cbe = new ClassBodyEvaluator();
 cbe.setClassName(className);
 cbe.setExtendedType(optionalExtendedType);
 cbe.setImplementedTypes(implementedTypes);
 cbe.setParentClassLoader(optionalParentClassLoader);
 cbe.cook(scanner);

• A class declaration with the configured name, superclass and interfaces
• A method declaration with the given return type, name, parameter names and values and thrown exceptions

For an explanation of the "fast class body evaluator" concept, see the class description.
Parameters:
  scanner - Source of class body tokens
Parameters:
  optionalBaseType - Base type to extend/implement
Parameters:
  optionalParentClassLoader - Used to load referenced classes, defaults to the current thread's "context class loader" an object that extends/implements the given optionalBaseType
See Also:   ClassBodyEvaluator

For an explanation of the "fast class body evaluator" concept, see the class description.
Parameters:
  scanner - Source of class body tokens
Parameters:
  className - Name of generated class
Parameters:
  optionalExtendedType - Class to extend
Parameters:
  implementedTypes - Interfaces to implement
Parameters:
  optionalParentClassLoader - Used to load referenced classes, defaults to the current thread's "context class loader" an object that extends the optionalExtendedType and implements the given implementedTypes
See Also:   ClassBodyEvaluator

This method must only be called after ClassBodyEvaluator.cook(Scanner) .

This method must not be called for instances of derived classes.

One reason to use this function is to have a class name in a non-default package, which can be relevant when types and members with DEFAULT accessibility are accessed.

Example: sc.setDefaultImports(new String[] { "java.util.Map", "java.io.*" });

The common reason to set a base class for an evaluator is that the generated class can directly access the base superclass's (non-private) members.