Exemplo n.º 1
0
  public static void main(final String args[]) throws Exception {

    // Generates the bytecode corresponding to the following Java class:
    //
    // public class Example {
    // public static void main (String[] args) {
    // System.out.println("Hello world!");
    // }
    // }

    // creates a ClassWriter for the Example public class,
    // which inherits from Object
    ClassWriter cw = new ClassWriter(0);
    cw.visit(V1_1, ACC_PUBLIC, "Example", null, "java/lang/Object", null);

    // creates a MethodWriter for the (implicit) constructor
    MethodVisitor mw = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
    // pushes the 'this' variable
    mw.visitVarInsn(ALOAD, 0);
    // invokes the super class constructor
    mw.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V");
    mw.visitInsn(RETURN);
    // this code uses a maximum of one stack element and one local variable
    mw.visitMaxs(1, 1);
    mw.visitEnd();

    // creates a MethodWriter for the 'main' method
    mw = cw.visitMethod(ACC_PUBLIC + ACC_STATIC, "main", "([Ljava/lang/String;)V", null, null);
    // pushes the 'out' field (of type PrintStream) of the System class
    mw.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
    // pushes the "Hello World!" String constant
    mw.visitLdcInsn("Hello world!");
    // invokes the 'println' method (defined in the PrintStream class)
    mw.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V");
    mw.visitInsn(RETURN);
    // this code uses a maximum of two stack elements and two local
    // variables
    mw.visitMaxs(2, 2);
    mw.visitEnd();

    // gets the bytecode of the Example class, and loads it dynamically
    byte[] code = cw.toByteArray();

    FileOutputStream fos = new FileOutputStream("Example.class");
    fos.write(code);
    fos.close();

    Helloworld loader = new Helloworld();
    Class<?> exampleClass = loader.defineClass("Example", code, 0, code.length);

    // uses the dynamically generated class to print 'Helloworld'
    exampleClass.getMethods()[0].invoke(null, new Object[] {null});

    // ------------------------------------------------------------------------
    // Same example with a GeneratorAdapter (more convenient but slower)
    // ------------------------------------------------------------------------

    cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
    cw.visit(V1_1, ACC_PUBLIC, "Example", null, "java/lang/Object", null);

    // creates a GeneratorAdapter for the (implicit) constructor
    Method m = Method.getMethod("void <init> ()");
    GeneratorAdapter mg = new GeneratorAdapter(ACC_PUBLIC, m, null, null, cw);
    mg.loadThis();
    mg.invokeConstructor(Type.getType(Object.class), m);
    mg.returnValue();
    mg.endMethod();

    // creates a GeneratorAdapter for the 'main' method
    m = Method.getMethod("void main (String[])");
    mg = new GeneratorAdapter(ACC_PUBLIC + ACC_STATIC, m, null, null, cw);
    mg.getStatic(Type.getType(System.class), "out", Type.getType(PrintStream.class));
    mg.push("Hello world!");
    mg.invokeVirtual(Type.getType(PrintStream.class), Method.getMethod("void println (String)"));
    mg.returnValue();
    mg.endMethod();

    cw.visitEnd();

    code = cw.toByteArray();
    loader = new Helloworld();
    exampleClass = loader.defineClass("Example", code, 0, code.length);

    // uses the dynamically generated class to print 'Helloworld'
    exampleClass.getMethods()[0].invoke(null, new Object[] {null});
  }
Exemplo n.º 2
0
  public static byte[] createPojo(
      String className, ASMProperty[] properties, Class parent, Class[] interfaces, String srcName)
      throws PageException {
    className = className.replace('.', '/');
    className = className.replace('\\', '/');
    className = ListUtil.trim(className, "/");
    String[] inter = null;
    if (interfaces != null) {
      inter = new String[interfaces.length];
      for (int i = 0; i < inter.length; i++) {
        inter[i] = interfaces[i].getName().replace('.', '/');
      }
    }
    // CREATE CLASS
    ClassWriter cw = ASMUtil.getClassWriter();
    cw.visit(
        Opcodes.V1_6,
        Opcodes.ACC_PUBLIC,
        className,
        null,
        parent.getName().replace('.', '/'),
        inter);
    String md5;
    try {
      md5 = createMD5(properties);
    } catch (Throwable t) {
      md5 = "";
      t.printStackTrace();
    }

    FieldVisitor fv =
        cw.visitField(
            Opcodes.ACC_PUBLIC + Opcodes.ACC_FINAL + Opcodes.ACC_STATIC,
            "_md5_",
            "Ljava/lang/String;",
            null,
            md5);
    fv.visitEnd();

    // Constructor
    GeneratorAdapter adapter =
        new GeneratorAdapter(Opcodes.ACC_PUBLIC, CONSTRUCTOR_OBJECT, null, null, cw);
    adapter.loadThis();
    adapter.invokeConstructor(toType(parent, true), CONSTRUCTOR_OBJECT);
    adapter.returnValue();
    adapter.endMethod();

    // properties
    for (int i = 0; i < properties.length; i++) {
      createProperty(cw, className, properties[i]);
    }

    // complexType src
    if (!StringUtil.isEmpty(srcName)) {
      GeneratorAdapter _adapter =
          new GeneratorAdapter(
              Opcodes.ACC_PUBLIC + Opcodes.ACC_FINAL + Opcodes.ACC_STATIC,
              _SRC_NAME,
              null,
              null,
              cw);
      _adapter.push(srcName);
      _adapter.returnValue();
      _adapter.endMethod();
    }

    cw.visitEnd();
    return cw.toByteArray();
  }