【原】Android插件化开发基础之Java反射机制研究

陈喻 2021-10-19

展开全文

一、获得Class对象

Class<?> c = Class.forName("classname");   抛出ClassNotFoundException

二、获得实现接口

Class<?> inters[] = c.getInterfaces();
for(int i=0;i<inters.length;i++){
    System.out.print(inters[i].getName()+" ");        //getName()方法为取得接口名称；
}

三、获得父类

Class<?> superClass  = c.getSuperclass();     //获得父类
String name  = superClass.getName();    //获得父类名称

四、取得构造方法

Constructor cons[] = c.getConstructors();         //获得公开的构造方法
Constructor dcons[] = c.getDeclaredConstructors();        //获得全部构造方法
String modifier = Modifier.toString(cons[i].getModifiers());   //获得访问权限
String name = cons[i].getName();            //获得构造方法名称
Class<?> params[] = cons[i].getParameterTypes();        //获得参数类型对象

五、获得Method

Method ms[] = c.getMethods();                        //返回公共的全部方法，包括继承方法
Method dms[] = c.getDeclaredMethods();        //返回本类全部方法，不包括继承的方法
Class<?> rt = ms[i].getReturnType();
Class<?>params[] = ms[i].getParameterTypes();
String name = ms[i].getName();
String modifier = Modifier.toString(ms[i].getModifiers());
Class<?>ex[] = ms[i].getExceptionTypes();        //获得异常
String name = ex[i].getName();            //获得异常名称

六、获得Field

Field fs[] = c.getFields();                    //获得公共属性，包括继承属性
Field dfs[] = c.getDeclaredFields();    // 获得本类全部属性
Class<?> type = fs[i].getType();        //获得属性的类型对象
String name = fs[i].getName();        //获得属性的名称
String modifier = Modifier.toString(fs[i].getModifiers());

七、通过反射创建一个对象

(1)
Class<?> c = Class.forName("Person");
Person p = (Person)c.newInstance();
(2)
Constructor con = c1.getConstructor(Class....param);
Object obj = con.newInstance(Object obj);  //根据构造函数创建一个实例

八、Constructor创建对象
Class c = Class.forName("Person");
Constructor<?> cons[] = c.getConstructors();
Person p = (Person)cons[0].newInstance("xiazdong",15);
注：如果调用的构造函数为私有，则需要c.setAccessible(true);

九、调用特定方法
Method m = c1.getMethod("funcname",Class<?>...c); //funcname表示调用方法的名称，c表示参数的Class对象
例如：Method m = c1.getMethod("fun",String.class,int.class); 表示调用fun（String,int）;函数
Object obj = m.invoke(c1.newInstance(),"xiazdong",20); //如果有返回值，则invoke函数返回；
注：如果是调用静态的方法，则不需要设置对象；
Object obj = m.invoke(null,"xiazdong");

注：如果参数中有数组，比如 public static void main(String[]args);
则
Method m = c1.getMethod("main",String[].class);
m.invoke(null,(Object)new String[]{"aa","bb"});是对的；
m.invoke(null,new String[]{"aa","bb"}); 会调用 main(String,String);函数；

十、调用特定属性
Field f = c1.getDeclaredField("name"); //返回name属性
f.setAccessible(true); //私有属性可见
String name = (String)f.get(Object obj); //返回obj对象的name属性的值
f.set(Object obj,String n); //设置obj对象的name属性为n值；

十一、操作数组
int tmp[] = {1,2,3};
Class<?> c = tmp.getClass().getComponentType();
Array.getLength(tmp); //tmp数组的长度
c.getName(); //获得数组类型名称
Array.get(Object obj,int index); //获得obj数组的index索引的数值
Array.set(Object obj,int index,VALUE); //设置obj数组的index索引的数值为value；
Object obj = Array.newInstance(c,length); //c为数组的类型，length为数组的长度；obj为返回的数组对象；

import java.lang.reflect.*;  
public class GetMethodDemo01{  
    public static void main(String args[])throws Exception{  
        Class<?> c1 = Class.forName("Person");  
        Method m = c1.getMethod("sayHello");  
        m.invoke(c1.newInstance());  
        Method m2 = c1.getMethod("sayHello2",String.class,int.class);  
        String str = (String)m2.invoke(c1.newInstance(),"xiazdong",123);  
        System.out.println(str);  
        Field nameField = c1.getDeclaredField("name");  
        Field ageField = c1.getDeclaredField("age");  
        nameField.setAccessible(true);  
        ageField.setAccessible(true);  
        Person obj = (Person)c1.newInstance();  
        obj.setName("xzdong");  
        obj.setAge(12);  
        System.out.println(nameField.get(obj));  
        System.out.println(ageField.get(obj));  
        Method setName = c1.getMethod("setName",String.class);  
        setName.invoke(obj,"changed");  
        Method getName = c1.getMethod("getName");  
        System.out.println(getName.invoke(obj));  
  
        int tmp[] = {1,2,3};  
        Class<?> c3 = tmp.getClass().getComponentType();  
        System.out.println(c3.getName());  
        System.out.println("第一个数："+Array.get(tmp,0));  
        Array.set(tmp,0,5);  
        System.out.println("第一个数："+Array.get(tmp,0));  
  
        Object arr = Array.newInstance(c3,5);  
        System.arraycopy(tmp,0,arr,0,Array.getLength(tmp));  
        System.out.println(Array.get(arr,2));  
        System.out.println(Array.get(arr,3));  
    }  
}

import java.lang.reflect.*;
public class GetMethodDemo01{
public static void main(String args[])throws Exception{
Class<?> c1 = Class.forName("Person");
Method m = c1.getMethod("sayHello");
m.invoke(c1.newInstance());
Method m2 = c1.getMethod("sayHello2",String.class,int.class);
String str = (String)m2.invoke(c1.newInstance(),"xiazdong",123);
System.out.println(str);
Field nameField = c1.getDeclaredField("name");
Field ageField = c1.getDeclaredField("age");
nameField.setAccessible(true);
ageField.setAccessible(true);
Person obj = (Person)c1.newInstance();
obj.setName("xzdong");
obj.setAge(12);
System.out.println(nameField.get(obj));
System.out.println(ageField.get(obj));
Method setName = c1.getMethod("setName",String.class);
setName.invoke(obj,"changed");
Method getName = c1.getMethod("getName");
System.out.println(getName.invoke(obj));

int tmp[] = {1,2,3};
Class<?> c3 = tmp.getClass().getComponentType();
System.out.println(c3.getName());
System.out.println("第一个数："+Array.get(tmp,0));
Array.set(tmp,0,5);
System.out.println("第一个数："+Array.get(tmp,0));

Object arr = Array.newInstance(c3,5);
System.arraycopy(tmp,0,arr,0,Array.getLength(tmp));
System.out.println(Array.get(arr,2));
System.out.println(Array.get(arr,3));
}
}

import java.lang.reflect.*;  
interface China{  
    public static final String NAME = "CHINA";  
    public int AGE = 60;  
    public void sayHello();  
    public String sayHello2(String name,int age);  
}  
class Person implements China{  
    private String name;  
    private int age;  
    public String getName(){  
        return name;  
    }  
    public void setName(String name){  
        this.name = name;  
    }  
    public int getAge(){  
        return age;  
    }  
    public void setAge(int age){  
        this.age = age;  
    }  
    public void sayHello(){  
        System.out.println(NAME+"  "+AGE);  
    }  
    public String sayHello2(String name,int age){  
        return name+" "+age;  
    }  
}

import java.lang.reflect.*;  
interface China{  
    public static final String NAME = "CHINA";  
    public int AGE = 60;  
    public void sayHello();  
    public String sayHello2(String name,int age);  
}  
class Person implements China{  
    private String name;  
    private int age;  
    public String getName(){  
        return name;  
    }  
    public void setName(String name){  
        this.name = name;  
    }  
    public int getAge(){  
        return age;  
    }  
    public void setAge(int age){  
        this.age = age;  
    }  
    public void sayHello(){  
        System.out.println(NAME+"  "+AGE);  
    }  
    public String sayHello2(String name,int age){  
        return name+" "+age;  
    }  
}