method.invoke,methodinvoke方法
Method对象中invoke方法中第一个参数表示____
invoke方法的第一个参数是一个对象。
此对象可以为：①方法持有者；②方法持有者的继承者。
例子：父类有方法
public?class?Father?{
????public?void?say(String?name){
????????System.out.println("我是father叫"+name);
????}
}
子类有方法
public?class?Son?extends?Father?{
????@Override
????public?void?say(String?name){
????????System.out.println("我是son我叫"+name);
????}
}
测试类
public?class?TestInvoke?{
????public?void?test()?throws?Exception?{
????????Class?clazz?=?Class.forName("CloneObject.Father");//反射父类
????????Father?father?=?new?Father();//实例化父类
????????Son?son?=?new?Son();//实例化子类
????????Object?object=clazz.newInstance();//获得一个新的父类对象
????????
????????Method?method?=?clazz.getMethod("say",String.class);
????????method.invoke(father,"爸爸");
????????method.invoke(son,"孩子");
????????method.invoke(object,"新的父亲");
????}
????public?static?void?main(String[]?args)?throws?Exception?{
????????new?TestInvoke().test();
????}
}
结果
我是father叫爸爸
我是son我叫孩子
我是father叫新的父亲
java Method invoke 抛出异常
InvocationTargetException异常由Method.invoke(obj, args...)方法抛出。当被调用的方法的内部抛出了异常而没有被捕获时，将由此异常接收。
示例：
package com.zzj.test.reflect;
public class Reflect {
public void run(int i) throws ZeroException {
B b = new B();
b.run(i);
}
}
class B {
public void run(int i) throws ZeroException {
if (i 0) {
throw new ZeroException("参数不能小于零！");
}
System.out.println("参数：" + i);
}
}
class ZeroException extends Exception {
private static final long serialVersionUID = 1L;
private String detailMessage;
public ZeroException(String detailMessage) {
this.detailMessage = detailMessage;
}
public String getMessage() {
return detailMessage;
}
}
测试：
package com.zzj.test.reflect;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class Test {
public static void main(String[] args) {
try {
Class? clazz = Class.forName("com.zzj.test.reflect.Reflect");
Method method = clazz.getMethod("run", int.class);
method.invoke(clazz.newInstance(), -1);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SecurityException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
System.out.println("此处接收被调用方法内部未被捕获的异常");
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
}
}
}
输出：
此处接收被调用方法内部未被捕获的异常
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.zzj.test.reflect.Test.main(Test.java:11)
Caused by: com.zzj.test.reflect.ZeroException: 参数不能小于零！
at com.zzj.test.reflect.B.run(Reflect.java:13)
at com.zzj.test.reflect.Reflect.run(Reflect.java:6)
... 5 more
也可以直接打印目标异常：
package com.zzj.test.reflect;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class Test {
public static void main(String[] args) {
try {
Class? clazz = Class.forName("com.zzj.test.reflect.Reflect");
Method method = clazz.getMethod("run", int.class);
method.invoke(clazz.newInstance(), -1);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SecurityException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
System.out.println("此处接收被调用方法内部未被捕获的异常");
Throwable t = e.getTargetException();// 获取目标异常
t.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
}
}
}
输出：
此处接收被调用方法内部未被捕获的异常
com.zzj.test.reflect.ZeroException: 参数不能小于零！
at com.zzj.test.reflect.B.run(Reflect.java:13)
at com.zzj.test.reflect.Reflect.run(Reflect.java:6)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.zzj.test.reflect.Test.main(Test.java:11)
method的invoke方法怎么用
public?class?Names?{
?public?String?firstName?=?"Callan";
?public?String?lastName?=?"Wang";
?
?public?String?getFullName(){
??return?firstName?+?"?"?+?lastName;
?}
?
?public?String?getFullName(String?firstName,String?lastName){
??return?firstName?+?"?"?+?lastName;
?}
}
?
?
?
import?java.lang.reflect.InvocationTargetException;
import?java.lang.reflect.Method;
public?class?Test?{
?
?public?static?void?main(String[]?args)?throws?SecurityException,?NoSuchMethodException,?IllegalArgumentException,?IllegalAccessException,?InvocationTargetException?{
??
??Names?methods?=?new?Names();
?
??//?调用getFullName()方法
??Method?method1?=?methods.getClass().getMethod("getFullName");
??Object?obj1?=?method1.invoke(methods,?null);
??System.out.println(obj1);
??
??//?调用getFullName(String?firstName,String?lastName)方法
??Method?method2?=?methods.getClass().getMethod("getFullName",?new?Class[]{String.class,String.class});//方法带有两个String类型的参数
??//?invoke(从中调用基础方法的对象,用于方法调用的参数)
??Object?obj2?=?method2.invoke(methods,?new?String[]{"Callan","Wang"});
??System.out.println(obj2);
?}
}
如何把method.invoke后的返回值转成数组或集合类型
Java code
Object array = method.invoke(obj, new Object[]{});
int length = java.lang.reflect.Array.getLength(array);
ListObject list = new ArrayListObject();
for (int i=0; ilength; i++) {
list.add(java.lang.reflect.Array.get(array, i));
}
就是这样
java反射中method类中的invoke方法是做什么的，他有什么作用？
首先Method类代表一个方法，所以invoke（调用）就是调用Method类代表的方法。它可以让你实现动态调用，例如你可以动态的传人参数。下面是一个简单的例子。
public?class?MethodTest
{
????public?static?void?main(String[]?args)
????{
????????String?[]?names?={"tom","tim","allen","alice"};
????????Class??clazz?=?Test.class;
????????try
????????{
????????????Method?method?=?clazz.getMethod("sayHi",?String.class);
????????????for(String?name:names)
????????????????method.invoke(clazz.newInstance(),name);
????????}?catch?(NoSuchMethodException?e)
????????{
????????????e.printStackTrace();
????????}?catch?(IllegalAccessException?e)
????????{
????????????e.printStackTrace();
????????}?catch?(IllegalArgumentException?e)
????????{
????????????e.printStackTrace();
????????}?catch?(InvocationTargetException?e)
????????{
????????????e.printStackTrace();
????????}?catch?(InstantiationException?e)
????????{
????????????e.printStackTrace();
????????}
????}
}
class?Test
{
????public?void?sayHi(String?name)
????{
????????System.out.println("Hi?"+name);
????}
}