Example usage for org.objectweb.asm Opcodes ALOAD

List of usage examples for org.objectweb.asm Opcodes ALOAD

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In this page you can find the example usage for org.objectweb.asm Opcodes ALOAD.

Prototype

int ALOAD

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Usage

From source file:com.nginious.http.serialize.XmlSerializerCreator.java

License:Apache License

/**
 * Creates bytecode which implements the {@link XmlSerializer#serializeProperties(javax.xml.transform.sax.TransformerHandler, Object)}
 * method for the serializer class being created.
 * /*  w  w w.j  a  v  a2  s .  c  o  m*/
 * @param writer class byte code writer
 * @param intBeanClazzName binary name of serializer class being generated
 * @return a method visitor for writing bytecode inside the generated method
 */
private MethodVisitor createSerializeMethod(ClassWriter writer, String intBeanClazzName) {
    String[] exceptions = { "com/nginious/serialize/SerializerException" };
    MethodVisitor visitor = writer.visitMethod(Opcodes.ACC_PUBLIC, "serializeProperties",
            "(Ljavax/xml/transform/sax/TransformerHandler;Ljava/lang/Object;)V", null, exceptions);
    visitor.visitCode();

    Label label = new Label();
    visitor.visitVarInsn(Opcodes.ALOAD, 2);
    visitor.visitJumpInsn(Opcodes.IFNONNULL, label);
    visitor.visitInsn(Opcodes.RETURN);
    visitor.visitLabel(label);
    visitor.visitVarInsn(Opcodes.ALOAD, 0);
    visitor.visitVarInsn(Opcodes.ALOAD, 2);
    visitor.visitTypeInsn(Opcodes.CHECKCAST, intBeanClazzName);
    visitor.visitIntInsn(Opcodes.ASTORE, 3);
    return visitor;
}

From source file:com.nginious.http.xsp.DocumentPart.java

License:Apache License

/**
 * Creates bytecode for this document tag part using the specified class writer and method visitor.
 * /*ww  w  . java 2s  .co  m*/
 * @param intClassName the binary class name of the class being created
 * @param writer the class writer
 * @param visitor the method visitor
 * @throws XspException if unable to create bytecode
 */
void compile(String intClassName, ClassWriter writer, MethodVisitor visitor) throws XspException {
    // 0 = this, 1 = HttpRequest, 2 = HttpResponse, 3 = StringBuffer

    // StringBuffer buffer = new StringBuffer();
    visitor.visitTypeInsn(Opcodes.NEW, "java/lang/StringBuffer");
    visitor.visitInsn(Opcodes.DUP);
    visitor.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/StringBuffer", "<init>", "()V");
    visitor.visitVarInsn(Opcodes.ASTORE, 3);

    for (XspPart part : contentParts) {
        part.compile(intClassName, writer, visitor);
    }

    // response.setContentLength(buffer.length());
    visitor.visitVarInsn(Opcodes.ALOAD, 2);
    visitor.visitVarInsn(Opcodes.ALOAD, 3);
    visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/StringBuffer", "length", "()I");
    visitor.visitMethodInsn(Opcodes.INVOKEINTERFACE, "com/nginious/http/HttpResponse", "setContentLength",
            "(I)V");

    // response.addHeader(contentType);
    String contentType = getMetaContent("Content-Type");

    if (contentType == null) {
        contentType = "application/unknown";
    }

    visitor.visitVarInsn(Opcodes.ALOAD, 2);
    visitor.visitLdcInsn("Content-Type");
    visitor.visitLdcInsn(contentType);
    visitor.visitMethodInsn(Opcodes.INVOKEINTERFACE, "com/nginious/http/HttpResponse", "addHeader",
            "(Ljava/lang/String;Ljava/lang/String;)V");

    // PrintWriter writer = response.getWriter();
    // writer.print(buffer.toString());
    visitor.visitVarInsn(Opcodes.ALOAD, 2);
    visitor.visitMethodInsn(Opcodes.INVOKEINTERFACE, "com/nginious/http/HttpResponse", "getWriter",
            "()Ljava/io/PrintWriter;");
    visitor.visitVarInsn(Opcodes.ALOAD, 3);
    visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/StringBuffer", "toString",
            "()Ljava/lang/String;");
    visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/io/PrintWriter", "print", "(Ljava/lang/String;)V");
}

From source file:com.nginious.http.xsp.expr.EqualsOperator.java

License:Apache License

/**
 * Compiles bytecode for evaluating this equals operator producing
 * a string as result. The specified method visitor is used for generating
 * bytecode.// w  ww. ja  v a 2s. c  o  m
 * 
 * @param visitor the method visitor
 */
private void compileString(MethodVisitor visitor) {
    value1.compile(visitor, Type.STRING);
    visitor.visitVarInsn(Opcodes.ASTORE, 1);
    value2.compile(visitor, Type.STRING);
    visitor.visitVarInsn(Opcodes.ASTORE, 2);
    Label nullLabel = new Label();
    Label notNullLabel = new Label();

    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitJumpInsn(Opcodes.IFNULL, nullLabel);
    visitor.visitVarInsn(Opcodes.ALOAD, 2);
    visitor.visitJumpInsn(Opcodes.IFNULL, nullLabel);

    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitVarInsn(Opcodes.ALOAD, 2);
    visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/Object", "equals", "(Ljava/lang/Object;)Z");
    visitor.visitJumpInsn(Opcodes.GOTO, notNullLabel);

    visitor.visitLabel(nullLabel);
    visitor.visitLdcInsn(false);

    visitor.visitLabel(notNullLabel);
}

From source file:com.nginious.http.xsp.expr.ExpressionCompiler.java

License:Apache License

/**
 * Creates a compiled expression from the specified tree value node expression. The class bytecode for the 
 * compiled expression is generated at runtime.
 * //  w ww .j  a  v  a  2  s  . co m
 * @param uncompiled the uncompiled tree value node expression
 * @return the compiled expression
 * @throws ExpressionException if unable to compile expression
 */
public Expression compile(TreeExpression uncompiled) throws ExpressionException {
    ClassWriter writer = new ClassWriter(0);

    // Create class
    String className = classBaseName + classNameCounter.getAndIncrement();
    String classIdentifier = className.replace('.', '/');
    writer.visit(Opcodes.V1_6, Opcodes.ACC_PUBLIC, classIdentifier, "L" + classIdentifier + ";",
            "com/nginious/http/xsp/expr/Expression", null);

    // Create constructor
    MethodVisitor visitor = writer.visitMethod(Opcodes.ACC_PROTECTED, "<init>", "()V", null, null);
    visitor.visitCode();
    visitor.visitVarInsn(Opcodes.ALOAD, 0);
    visitor.visitMethodInsn(Opcodes.INVOKESPECIAL, "com/nginious/http/xsp/expr/Expression", "<init>", "()V");
    visitor.visitInsn(Opcodes.RETURN);
    visitor.visitMaxs(1, 1);
    visitor.visitEnd();

    // protected abstract boolean evaluateBoolean();
    visitor = writer.visitMethod(Opcodes.ACC_PROTECTED, "evaluateBoolean", "()Z", null, null);

    if (uncompiled.getType() == Type.BOOLEAN) {
        uncompiled.compile(visitor);
    } else if (uncompiled.getType() == Type.DOUBLE) {
        visitor.visitVarInsn(Opcodes.ALOAD, 0); // this
        visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, classIdentifier, "evaluateDouble", "()D");

        Label endLabel = new Label();
        Label falseLabel = new Label();
        visitor.visitLdcInsn(0.0d);
        visitor.visitInsn(Opcodes.DCMPL);
        visitor.visitJumpInsn(Opcodes.IFEQ, falseLabel);
        visitor.visitLdcInsn(true);
        visitor.visitJumpInsn(Opcodes.GOTO, endLabel);
        visitor.visitLabel(falseLabel);
        visitor.visitLdcInsn(false);
        visitor.visitLabel(endLabel);
    } else if (uncompiled.getType() == Type.INT) {
        visitor.visitVarInsn(Opcodes.ALOAD, 0); // this
        visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, classIdentifier, "evaluateInt", "()I");

        Label endLabel = new Label();
        Label falseLabel = new Label();
        visitor.visitLdcInsn(0);
        visitor.visitJumpInsn(Opcodes.IFNE, falseLabel);
        visitor.visitLdcInsn(true);
        visitor.visitJumpInsn(Opcodes.GOTO, endLabel);
        visitor.visitLabel(falseLabel);
        visitor.visitLdcInsn(false);
        visitor.visitLabel(endLabel);
    } else if (uncompiled.getType() == Type.STRING) {
        visitor.visitVarInsn(Opcodes.ALOAD, 0); // this
        visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, classIdentifier, "evaluateString",
                "()Ljava/lang/String;");
        visitor.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Boolean", "parseBoolean",
                "(Ljava/lang/String;)Z");
    }

    visitor.visitInsn(Opcodes.IRETURN);
    visitor.visitMaxs(5, 5);
    visitor.visitEnd();

    // protected abstract int evaluateInt();
    visitor = writer.visitMethod(Opcodes.ACC_PROTECTED, "evaluateInt", "()I", null, null);

    if (uncompiled.getType() == Type.BOOLEAN) {
        visitor.visitVarInsn(Opcodes.ALOAD, 0); // this
        visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, classIdentifier, "evaluateBoolean", "()Z");

        Label endLabel = new Label();
        Label falseLabel = new Label();
        visitor.visitJumpInsn(Opcodes.IFEQ, falseLabel);
        visitor.visitLdcInsn(1);
        visitor.visitJumpInsn(Opcodes.GOTO, endLabel);
        visitor.visitLabel(falseLabel);
        visitor.visitLdcInsn(0);
        visitor.visitLabel(endLabel);
    } else if (uncompiled.getType() == Type.DOUBLE) {
        visitor.visitVarInsn(Opcodes.ALOAD, 0); // this
        visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, classIdentifier, "evaluateDouble", "()D");
        visitor.visitInsn(Opcodes.D2I);
    } else if (uncompiled.getType() == Type.INT) {
        uncompiled.compile(visitor);
    } else if (uncompiled.getType() == Type.STRING) {
        visitor.visitVarInsn(Opcodes.ALOAD, 0); // this
        visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, classIdentifier, "evaluateString",
                "()Ljava/lang/String;");
        visitor.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Integer", "parseInt", "(Ljava/lang/String;)I");
    }

    visitor.visitInsn(Opcodes.IRETURN);
    visitor.visitMaxs(5, 5);
    visitor.visitEnd();

    // protected abstract double evaluateDouble();
    visitor = writer.visitMethod(Opcodes.ACC_PROTECTED, "evaluateDouble", "()D", null, null);

    if (uncompiled.getType() == Type.BOOLEAN) {
        visitor.visitVarInsn(Opcodes.ALOAD, 0); // this
        visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, classIdentifier, "evaluateBoolean", "()Z");

        Label endLabel = new Label();
        Label falseLabel = new Label();
        visitor.visitJumpInsn(Opcodes.IFEQ, falseLabel);
        visitor.visitLdcInsn(1.0d);
        visitor.visitJumpInsn(Opcodes.GOTO, endLabel);
        visitor.visitLabel(falseLabel);
        visitor.visitLdcInsn(0.0d);
        visitor.visitLabel(endLabel);
    } else if (uncompiled.getType() == Type.DOUBLE) {
        uncompiled.compile(visitor);
    } else if (uncompiled.getType() == Type.INT) {
        visitor.visitVarInsn(Opcodes.ALOAD, 0); // this
        visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, classIdentifier, "evaluateInt", "()I");
        visitor.visitInsn(Opcodes.I2D);
    } else if (uncompiled.getType() == Type.STRING) {
        visitor.visitVarInsn(Opcodes.ALOAD, 0); // this
        visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, classIdentifier, "evaluateString",
                "()Ljava/lang/String;");
        visitor.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Double", "parseDouble",
                "(Ljava/lang/String;)D");
    }

    visitor.visitInsn(Opcodes.DRETURN);
    visitor.visitMaxs(5, 5);
    visitor.visitEnd();

    // protected abstract String evaluateString();
    visitor = writer.visitMethod(Opcodes.ACC_PROTECTED, "evaluateString", "()Ljava/lang/String;", null, null);

    if (uncompiled.getType() == Type.BOOLEAN) {
        visitor.visitVarInsn(Opcodes.ALOAD, 0); // this
        visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, classIdentifier, "evaluateBoolean", "()Z");
        visitor.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Boolean", "toString", "(Z)Ljava/lang/String;");
    } else if (uncompiled.getType() == Type.DOUBLE) {
        visitor.visitVarInsn(Opcodes.ALOAD, 0); // this
        visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, classIdentifier, "evaluateDouble", "()D");
        visitor.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Double", "toString", "(D)Ljava/lang/String;");
    } else if (uncompiled.getType() == Type.INT) {
        visitor.visitVarInsn(Opcodes.ALOAD, 0); // this
        visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, classIdentifier, "evaluateInt", "()I");
        visitor.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Integer", "toString", "(I)Ljava/lang/String;");
    } else if (uncompiled.getType() == Type.STRING) {
        uncompiled.compile(visitor);
    }

    visitor.visitInsn(Opcodes.ARETURN);
    visitor.visitMaxs(6, 6);
    visitor.visitEnd();

    // public abstract Type getType();        
    visitor = writer.visitMethod(Opcodes.ACC_PUBLIC, "getType", "()Lcom/nginious/http/xsp/expr/Type;", null,
            null);

    if (uncompiled.getType() == Type.BOOLEAN) {
        visitor.visitFieldInsn(Opcodes.GETSTATIC, "com/nginious/http/xsp/expr/Type", "BOOLEAN",
                "Lcom/nginious/http/xsp/expr/Type;");
        visitor.visitInsn(Opcodes.ARETURN);
    } else if (uncompiled.getType() == Type.DOUBLE) {
        visitor.visitFieldInsn(Opcodes.GETSTATIC, "com/nginious/http/xsp/expr/Type", "DOUBLE",
                "Lcom/nginious/http/xsp/expr/Type;");
        visitor.visitInsn(Opcodes.ARETURN);
    } else if (uncompiled.getType() == Type.INT) {
        visitor.visitFieldInsn(Opcodes.GETSTATIC, "com/nginious/http/xsp/expr/Type", "INT",
                "Lcom/nginious/http/xsp/expr/Type;");
        visitor.visitInsn(Opcodes.ARETURN);
    } else if (uncompiled.getType() == Type.STRING) {
        visitor.visitFieldInsn(Opcodes.GETSTATIC, "com/nginious/http/xsp/expr/Type", "STRING",
                "Lcom/nginious/http/xsp/expr/Type;");
        visitor.visitInsn(Opcodes.ARETURN);
    }

    visitor.visitMaxs(1, 1);
    visitor.visitEnd();

    try {
        writer.visitEnd();
        byte[] clazzBytes = writer.toByteArray();
        Class<?> clazz = loadClass(className, clazzBytes);
        return (Expression) clazz.newInstance();
    } catch (Exception e) {
        throw new ExpressionException("Can't instantiate compiled expression", e);
    }
}

From source file:com.nginious.http.xsp.expr.LeftFunction.java

License:Apache License

/**
 * Creates bytecode for evaluating this left function. The specified method visitor
 * and type are used for generating bytecode.
 * /*from   w  w w. j a v a2s .  c om*/
 * @param visitor the method visitor
 * @param type the type
 */
void compile(MethodVisitor visitor, Type type) {
    value.compile(visitor, Type.STRING);
    visitor.visitVarInsn(Opcodes.ASTORE, 1);

    Label nullLabel = new Label();
    Label notNullLabel = new Label();

    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitJumpInsn(Opcodes.IFNULL, nullLabel);

    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitLdcInsn(0);
    value2.compile(visitor, Type.INT);
    visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/String", "substring", "(II)Ljava/lang/String;");
    visitor.visitJumpInsn(Opcodes.GOTO, notNullLabel);

    visitor.visitLabel(nullLabel);
    visitor.visitInsn(Opcodes.ACONST_NULL);

    visitor.visitLabel(notNullLabel);
}

From source file:com.nginious.http.xsp.expr.LengthFunction.java

License:Apache License

/**
 * Creates bytecode for evaluating this function. The specified method
 * visitor is used to generate bytecode. The generated bytecode produces
 * a result of the specified type.//w w  w .ja  v a2 s.  c o m
 * 
 * @param visitor the method visitor
 * @param type the type
 */
void compile(MethodVisitor visitor, Type type) {
    value.compile(visitor, Type.STRING);
    visitor.visitVarInsn(Opcodes.ASTORE, 1);

    Label nullLabel = new Label();
    Label notNullLabel = new Label();

    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitJumpInsn(Opcodes.IFNULL, nullLabel);

    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/String", "length", "()I");
    visitor.visitJumpInsn(Opcodes.GOTO, notNullLabel);

    visitor.visitLabel(nullLabel);
    visitor.visitLdcInsn(0);

    visitor.visitLabel(notNullLabel);
}

From source file:com.nginious.http.xsp.expr.NotEqualsOperator.java

License:Apache License

/**
 * Compiles bytecode for evaluating this not equals operator producing
 * a string as result. The specified method visitor is used for generating
 * bytecode.//from   ww w .  j av  a  2 s.  c o  m
 * 
 * @param visitor the method visitor
 */
private void compileString(MethodVisitor visitor) {
    Label trueLabel = new Label();
    Label falseLabel = new Label();
    Label nullLabel = new Label();

    value1.compile(visitor, Type.STRING);
    visitor.visitVarInsn(Opcodes.ASTORE, 1);
    value2.compile(visitor, Type.STRING);
    visitor.visitVarInsn(Opcodes.ASTORE, 2);

    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitJumpInsn(Opcodes.IFNULL, nullLabel);
    visitor.visitVarInsn(Opcodes.ALOAD, 2);
    visitor.visitJumpInsn(Opcodes.IFNULL, nullLabel);

    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitVarInsn(Opcodes.ALOAD, 2);
    visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/Object", "equals", "(Ljava/lang/Object;)Z");
    visitor.visitJumpInsn(Opcodes.IFNE, falseLabel);

    visitor.visitLabel(nullLabel);
    visitor.visitLdcInsn(true);
    visitor.visitJumpInsn(Opcodes.GOTO, trueLabel);

    visitor.visitLabel(falseLabel);
    visitor.visitLdcInsn(false);

    visitor.visitLabel(trueLabel);
}

From source file:com.nginious.http.xsp.expr.RightFunction.java

License:Apache License

/**
 * Creates bytecode for evaluating this right function. The specified method visitor
 * and type are used for generating bytecode.
 * //w  w w .ja v a  2 s.  c o m
 * @param visitor the method visitor
 * @param type the type
 */
void compile(MethodVisitor visitor, Type type) {
    value.compile(visitor, Type.STRING);
    visitor.visitVarInsn(Opcodes.ASTORE, 1);

    Label nullLabel = new Label();
    Label notNullLabel = new Label();

    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitJumpInsn(Opcodes.IFNULL, nullLabel);

    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/String", "length", "()I");
    value2.compile(visitor, Type.INT);
    visitor.visitInsn(Opcodes.ISUB);
    visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/String", "substring", "(I)Ljava/lang/String;");
    visitor.visitJumpInsn(Opcodes.GOTO, notNullLabel);

    visitor.visitLabel(nullLabel);
    visitor.visitInsn(Opcodes.ACONST_NULL);

    visitor.visitLabel(notNullLabel);
}

From source file:com.nginious.http.xsp.expr.SubstrFunction.java

License:Apache License

/**
 * Creates bytecode for evaluating this substring function. The specified method visitor
 * and type are used for generating bytecode.
 * //from   w  w w.j  a v a 2s . co  m
 * @param visitor the method visitor
 * @param type the type
 */
void compile(MethodVisitor visitor, Type type) {
    value.compile(visitor, Type.STRING);
    visitor.visitVarInsn(Opcodes.ASTORE, 1);
    value2.compile(visitor, Type.INT);
    visitor.visitVarInsn(Opcodes.ISTORE, 2);
    value3.compile(visitor, Type.INT);
    visitor.visitVarInsn(Opcodes.ISTORE, 3);

    Label nullLabel = new Label();
    Label notNullLabel = new Label();

    // check for null string
    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitJumpInsn(Opcodes.IFNULL, nullLabel);

    // start < 0
    Label label1 = new Label();
    visitor.visitLdcInsn(0);
    visitor.visitVarInsn(Opcodes.ILOAD, 2);
    visitor.visitJumpInsn(Opcodes.IF_ICMPLT, label1);
    visitor.visitLdcInsn(0);
    visitor.visitVarInsn(Opcodes.ISTORE, 2);

    // start > value.length
    Label label2 = new Label();
    visitor.visitLabel(label1);
    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/String", "length", "()I");
    visitor.visitVarInsn(Opcodes.ILOAD, 2);
    visitor.visitJumpInsn(Opcodes.IF_ICMPGT, label2);
    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/String", "length", "()I");
    visitor.visitVarInsn(Opcodes.ISTORE, 2);

    // end < start
    Label label3 = new Label();
    visitor.visitLabel(label2);
    visitor.visitVarInsn(Opcodes.ILOAD, 2);
    visitor.visitVarInsn(Opcodes.ILOAD, 3);
    visitor.visitJumpInsn(Opcodes.IF_ICMPLT, label3);
    visitor.visitVarInsn(Opcodes.ILOAD, 2);
    visitor.visitVarInsn(Opcodes.ISTORE, 3);

    // end > value1.length
    Label label4 = new Label();
    visitor.visitLabel(label3);
    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/String", "length", "()I");
    visitor.visitVarInsn(Opcodes.ILOAD, 3);
    visitor.visitJumpInsn(Opcodes.IF_ICMPGT, label4);
    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/String", "length", "()I");
    visitor.visitVarInsn(Opcodes.ISTORE, 3);

    // substr
    visitor.visitLabel(label4);
    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitVarInsn(Opcodes.ILOAD, 2);
    visitor.visitVarInsn(Opcodes.ILOAD, 3);
    visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/String", "substring", "(II)Ljava/lang/String;");
    visitor.visitJumpInsn(Opcodes.GOTO, notNullLabel);

    visitor.visitLabel(nullLabel);
    visitor.visitInsn(Opcodes.ACONST_NULL);

    visitor.visitLabel(notNullLabel);

}

From source file:com.nginious.http.xsp.ForEachTagPart.java

License:Apache License

/**
 * Creates bytecode for this for each tag part using the specified class writer and method visitor.
 * //from   w  w  w .  j a va2 s. c  o m
 * @param intClassName the binary class name of the class being created
 * @param writer the class writer
 * @param visitor the method visitor
 * @throws XspException if unable to create bytecode
 */
void compile(String intClassName, ClassWriter writer, MethodVisitor visitor) throws XspException {
    if (this.setValue == null) {
        throw new XspException(
                "Attribute set is missing for tag + " + getName() + " at " + getLocationDescriptor());
    }

    if (this.varName == null) {
        throw new XspException(
                "Attribute var is missing for tag + " + getName() + " at " + getLocationDescriptor());
    }

    this.methodName = "forEach" + methodNameCounter.getAndIncrement();
    visitor.visitVarInsn(Opcodes.ALOAD, 0);
    visitor.visitVarInsn(Opcodes.ALOAD, 1);
    visitor.visitVarInsn(Opcodes.ALOAD, 2);
    visitor.visitVarInsn(Opcodes.ALOAD, 3);
    visitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, intClassName, this.methodName,
            "(Lcom/nginious/http/HttpRequest;Lcom/nginious/http/HttpResponse;Ljava/lang/StringBuffer;)V");
}