文章目录 1.概述
1.概述
因为要Java反射调用可变参数的方法，所以参考了这篇文章：https://www.cnblogs.com/huqingchen/p/5979936.html
但是测试过程中，有一点我不明白，就是反射调用可变参数的方法时，为什么一定要保证传入的参数数组长度为1，
然后如下
package com.java.reflect.demo;public class BaseObject { public void getObjectName() { System.out.println("BaseObject"); }}package com.java.reflect.demo;public class SubObject extends BaseObject { @Override public void getObjectName() { System.out.println("SubObject"); } public void getParamsLength(String... params) { System.out.println("param's length is:" + params.length); } public void getParamsLength(String param1, String param2) { System.out.println(param1 + "-" + param2); }}测试类如下
package com.java.reflect.demo;import org.junit.Assert;import org.junit.Test;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import static org.junit.Assert.*;public class ReflectToMulityParamsMethosTest { private static final String BASE_OBJECT_PATH = "com.java.reflect.demo.BaseObject"; private static final String SUB_OBJECT_PATH = "com.java.reflect.demo.SubObject"; /** * 测试点：测试反射调用可变参数的方法 */ @Test public void reflectToMulityParamsMethosTest1() throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException { Class sClazz = Class.forName(SUB_OBJECT_PATH); Object sObj = sClazz.newInstance();//子类实例 //2.反射调用可变参数的方法 Method changeMethod = sClazz.getDeclaredMethod("getParamsLength", String[].class); //可变参数必须这样封装，因为java反射内部实现做了参数个数为1的判断，如果参数长度不为1，则会抛出异常 String[] strParams = {"a","b","c"}; Object[] cParams = {strParams}; changeMethod.invoke(sObj, cParams); } /** * 测试点： * 参数为 1 * * 运行如下 * 0 * 1 * @throws ClassNotFoundException * @throws IllegalAccessException * @throws InstantiationException * @throws NoSuchMethodException * @throws InvocationTargetException */ @Test public void reflectToMulityParamsMethosTest2() throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException { Class sClazz = Class.forName(SUB_OBJECT_PATH); Object sObj = sClazz.newInstance();//子类实例 //2.反射调用可变参数的方法 Method changeMethod = sClazz.getDeclaredMethod("getParamsLength", String[].class); //可变参数必须这样封装，因为java反射内部实现做了参数个数为1的判断，如果参数长度不为1，则会抛出异常 String[] strParams = {}; System.out.println(strParams.length); Object[] cParams = {strParams}; System.out.println(cParams.length); changeMethod.invoke(sObj, cParams); } /** * 测试点：这个与上面差了一点点，然后一个报错 一个不报错 * 这里离的参数个数为0，上面的参数个数为1 * @throws ClassNotFoundException * @throws IllegalAccessException * @throws InstantiationException * @throws NoSuchMethodException * @throws InvocationTargetException */ @Test public void reflectToMulityParamsMethosTest3() throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException { Class sClazz = Class.forName(SUB_OBJECT_PATH); Object sObj = sClazz.newInstance();//子类实例 //2.反射调用可变参数的方法 Method changeMethod = sClazz.getDeclaredMethod("getParamsLength", String[].class); //可变参数必须这样封装，因为java反射内部实现做了参数个数为1的判断，如果参数长度不为1，则会抛出异常 Object[] cParams = {}; System.out.println(cParams.length); changeMethod.invoke(sObj, cParams); } /** * 测试点：测试反射调用可变参数的方法 */ @Test public void reflectToMulityParamsMethosTest() throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException { Class bClazz = Class.forName(BASE_OBJECT_PATH); Class sClazz = Class.forName(SUB_OBJECT_PATH); Object bObj = bClazz.newInstance();//父类实例 Object sObj = sClazz.newInstance();//子类实例 // 1.反射调用子类父类的重载方法 // 多态+动态绑定 Method bMethod = bClazz.getDeclaredMethod("getObjectName"); bMethod.invoke(bObj);//父类的bMethod调用父类的getObjectName() bMethod.invoke(sObj);//父类的bMethod调用子类的getObjectName(); Method sMethod = sClazz.getDeclaredMethod("getObjectName"); //不符合多态和动态绑定 // sMethod.invoke(bObj);//sMethod调用父类的getObjectName()，会报错：java.lang.IllegalArgumentException: object is not an instance of declaring class sMethod.invoke(sObj); //2.反射调用可变参数的方法 Method changeMethod = sClazz.getDeclaredMethod("getParamsLength", String[].class); //可变参数必须这样封装，因为java反射内部实现做了参数个数为1的判断，如果参数长度不为1，则会抛出异常 String[] strParams = {"a","b","c"}; Object[] cParams = {strParams}; changeMethod.invoke(sObj, cParams); //3.反射调用固定长度参数的方法 Method unChangeMethod1 = sClazz.getDeclaredMethod("getParamsLength", String.class,String.class); unChangeMethod1.invoke(sObj, "Hello","Java"); //也可以写成这样 Class[] clazzs = {String.class,String.class}; Method unChangeMethod2 = sClazz.getDeclaredMethod("getParamsLength", clazzs); unChangeMethod2.invoke(sObj, "Hello","Java"); //下面的这种调用形式也是可以的，不过会报警告 // String[] params1 = {"Hello","Java"}; // unChangeMethod1.invoke(sObj, params1); }}