ASMSupport教程4.10 instanceof操作符生成

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<p>instanceof是判断对象是否是某种类型的，我们可以看下下面的代码：</p> <div id="scid:9D7513F9-C04C-4721-824A-2B34F0212519:4f2d1c23-092c-4b0f-888f-8ada43241043" class="wlWriterEditableSmartContent" style="float: none; padding-bottom: 0px; padding-top: 0px; padding-left: 0px; margin: 0px; display: inline; padding-right: 0px"><pre class="brush: java; gutter: true; first-line: 1; tab-size: 4; toolbar: true; width: 665px; height: 295px;" style=" width: 665px; height: 295px;overflow: auto;">package generated.operators;

import java.io.PrintStream; import java.util.ArrayList; import java.util.HashMap; import java.util.List;

public class InstanceofOperatorGenerateExample { public static void main(String[] args) { System.out.println("String" instanceof CharSequence); System.out.println(new ArrayList() instanceof List); System.out.println(new HashMap() instanceof List); } }</pre><!-- Code inserted with Steve Dunn's Windows Live Writer Code Formatter Plugin. http://dunnhq.com --></div>

<p>我们知道，这段代码打印出来的是</p> <p>true</p> <p>true</p> <p>false</p> <p>下面我们用ASMSupport生成上面的代码</p> <div id="scid:9D7513F9-C04C-4721-824A-2B34F0212519:db04b8b1-814b-43de-b6a9-94197acd931e" class="wlWriterEditableSmartContent" style="float: none; padding-bottom: 0px; padding-top: 0px; padding-left: 0px; margin: 0px; display: inline; padding-right: 0px"><pre class="brush: java; gutter: true; first-line: 1; tab-size: 4; toolbar: true; width: 665px; height: 861px;" style=" width: 665px; height: 861px;overflow: auto;">package example.operators;

import java.util.ArrayList; import java.util.HashMap; import java.util.List;

import jw.asmsupport.block.method.common.StaticMethodBody; import jw.asmsupport.clazz.AClass; import jw.asmsupport.clazz.AClassFactory; import jw.asmsupport.creator.ClassCreator; import jw.asmsupport.definition.value.Value; import jw.asmsupport.definition.variable.LocalVariable;

import org.objectweb.asm.Opcodes;

import example.AbstractExample;

public class InstanceofOperatorGenerate1 extends AbstractExample {

public static void main(String[] args) {
    
    ClassCreator creator = new ClassCreator(Opcodes.V1_5, Opcodes.ACC_PUBLIC , "generated.operators.InstanceofOperatorGenerateExample", null, null);
	
	/*
	 * 生成一个main方法
	 */
	creator.createStaticMethod("main", new AClass[]{AClassFactory.getProductClass(String[].class)}, new String[]{"args"}, null, null,
			Opcodes.ACC_PUBLIC + Opcodes.ACC_STATIC, new StaticMethodBody(){

		@Override
		public void generateBody(LocalVariable... argus) {
			invoke(systemOut, "println", instanceOf(Value.value("String"), AClassFactory.getProductClass(CharSequence.class)));
			invoke(systemOut, "println", instanceOf(invokeConstructor(AClassFactory.getProductClass(ArrayList.class)),
					AClassFactory.getProductClass(List.class)));
			invoke(systemOut, "println", instanceOf(invokeConstructor(AClassFactory.getProductClass(HashMap.class)),
					AClassFactory.getProductClass(List.class)));
			runReturn();
		}
    });
	generate(creator);
}

}</pre><!-- Code inserted with Steve Dunn's Windows Live Writer Code Formatter Plugin. http://dunnhq.com --></div>

<p>这里面instanceof操作对于的方法是instanceOf，具体如下：</p> <p><strong><font color="#f79646">jw.asmsupport.block.ProgramBlock.instanceOf(Parameterized obj, AClass type)</font></strong> ,这个方法有两个参数：</p> <ol> <li>instanceof左边的参数，是一个对象。</li> <li>AClass类型，instanceof右边的参数。</li></ol> <p>AClass是ASMSupport的特有的类型，详细可以见博客<a href="http://www.wensiqun.com/2013/06/08/asmsupport_tutorial_1.html">ASMSupport教程1之动态生成接口</a>。</p> <p>执行这段代码，也是：</p> <p>true</p> <p>true</p> <p>false</p>

来源：oschina

链接：https://my.oschina.net/u/238125/blog/143695