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Android插件化开发基础之Java反射机制研究
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;
}
}
作者：chen.yu
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