二、JAVA反射机制--进阶篇详解
目录
一、Constructors
二、Methods
三、Getter and Setter
四、 Private fields and methods
六、 Dynamic Class Loading and Reloading
一、Constructors
包括构造方法的获得及实例化对象。
package design;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.text.Annotation;
import java.text.DateFormat.Field;
import java.util.Scanner;
import ch13.Student;
//import java.lang.reflect.Field;
public abstract class Main {
public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, InstantiationException {
String info="ch13.Student";
Class class1=Class.forName(info);
System.out.println(class1);
//获取类名
String ClassName=class1.getName();
Sop(ClassName);
//获取不带包名的类名
ClassName=class1.getSimpleName();
Sop(ClassName);
//获取构造函数
Constructor []constructors=class1.getConstructors();
for(Constructor c1:constructors)
{
Sop(c1);
}
//获取特定参数构造函数
Constructor constructor=class1.getConstructor(new Class[]{String.class,String.class,int.class});
Sop(constructor);
Sop("----");
//获取构造函数参数类型
Class []parameterTypes =constructor.getParameterTypes();
for(Class c2:parameterTypes)
{
Sop(c2);
}
for(Constructor c1:constructors)
{
Class []parameterType1 =c1.getParameterTypes();
for(Class c2:parameterTypes)
{
Sop(c2);
}
}
Sop("----");
//实例化一个对象并调用相关函数
Student stu=(Student)constructor.newInstance("20171789","pre",19);
stu.showInformation();
}
private static void Sop(Object className) {
// TODO Auto-generated method stub
System.out.println(className);
}
}
二、Methods
包括一些对象实例化以及方法的调用。
package design;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.text.Annotation;
import java.text.DateFormat.Field;
import java.util.Scanner;
import ch13.Student;
//import java.lang.reflect.Field;
public abstract class Main {
public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, InstantiationException {
String info="ch13.Student";
Class class1=Class.forName(info);
System.out.println(class1);
//获取类名
String ClassName=class1.getName();
Sop(ClassName);
//获取不带包名的类名
ClassName=class1.getSimpleName();
Sop(ClassName);
//获取指定类型的
Sop("---");
Method m1=class1.getDeclaredMethod("setName", String.class);
Sop(m1.getName());
Sop(m1);
m1=class1.getDeclaredMethod("setName1", String.class);
Sop(m1);
m1=class1.getDeclaredMethod("showInformation", null);
Sop(m1);
//一般getDeclared...可以得到任意类型的方法、成员
Sop("---");
//获取函数参数类型
Method m2s[]=class1.getDeclaredMethods();
for(Method m2:m2s)
{
Class []para=m2.getParameterTypes();
for(Class m3:para)
{
Sop(m3);
}
}
//获取函数返回值类型
for(Method m2:m2s)
{
Class m4=m2.getReturnType();
Sop(m4.getName());
}
//
Constructor c1=class1.getConstructor();
Object obj=c1.newInstance();
Student stu=(Student)obj;
Sop("---");
m1=class1.getMethod("setId", String.class);
stu.showInformation();
m1.invoke(obj, "2017");//调用函数---
stu.showInformation();
m1=class1.getMethod("setGrade", int.class);
m1.invoke(obj, 100);
stu.showInformation();
//这样就完成了各项信息的变化
/*//获取构造函数
Constructor []constructors=class1.getConstructors();
for(Constructor c1:constructors)
{
Sop(c1);
}
//获取特定参数构造函数
Constructor constructor=class1.getConstructor(new Class[]{String.class,String.class,int.class});
Sop(constructor);
Sop("----");
//获取构造函数参数类型
Class []parameterTypes =constructor.getParameterTypes();
for(Class c2:parameterTypes)
{
Sop(c2);
}
for(Constructor c1:constructors)
{
Class []parameterType1 =c1.getParameterTypes();
for(Class c2:parameterTypes)
{
Sop(c2);
}
}
Sop("----");
//实例化一个对象并调用相关函数
Student stu=(Student)constructor.newInstance("20171789","pre",19);
stu.showInformation();
*/
}
private static void Sop(Object className) {
// TODO Auto-generated method stub
System.out.println(className);
}
}
三、Getter and Setter
package design;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.text.Annotation;
import java.text.DateFormat.Field;
import java.util.Scanner;
import ch13.Student;
//import java.lang.reflect.Field;
public abstract class Main {
public static void main(String[] args)
throws ClassNotFoundException, NoSuchMethodException, SecurityException, IllegalAccessException,
IllegalArgumentException, InvocationTargetException, InstantiationException {
String info = "ch13.Student";
Class class1 = Class.forName(info);
System.out.println(class1);
// 获取类名
String ClassName = class1.getName();
Sop(ClassName);
// 获取不带包名的类名
ClassName = class1.getSimpleName();
Sop(ClassName);
Sop("下面是获取特定函数");
Method[] ms = class1.getMethods();
for (Method m : ms) {
if (isGetter(m)) {
Sop("isGetter：" + m);
} else if (isSetter(m)) {
Sop("isSetter：" + m);
}
}
Sop("---");
}
private static boolean isSetter(Method m) {
// TODO Auto-generated method stub
if (!m.getName().startsWith("get"))
return false;
else if (m.getParameterTypes().length != 0)
return false;
else if (void.class.equals(m.getReturnType()))
return false;
return true;
}
private static boolean isGetter(Method m) {
// TODO Auto-generated method stub
if (!m.getName().startsWith("set"))
return false;
else if (m.getParameterTypes().length != 1)
return false;
return true;
}
private static void Sop(Object className) {
// TODO Auto-generated method stub
System.out.println(className);
}
}
四、 Private fields and methods
在第一遍文章中已经演示过，这里只给出一个小荔枝。
package design;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.text.Annotation;
import java.text.DateFormat.Field;
import java.util.Scanner;
import ch13.Student;
//import java.lang.reflect.Field;
public abstract class Main {
public static void main(String[] args)
throws ClassNotFoundException, NoSuchMethodException, SecurityException, IllegalAccessException,
IllegalArgumentException, InvocationTargetException, InstantiationException {
String info = "ch13.Student";
Class class1 = Class.forName(info);
System.out.println(class1);
// 获取类名
String ClassName = class1.getName();
Sop(ClassName);
// 获取私有函数
Method privateMethod=class1.getDeclaredMethod("setName1", String.class);
privateMethod.setAccessible(true);
Object obj=class1.newInstance();
Student stu=(Student)obj;
String value=(String) privateMethod.invoke(stu, "haha");
Sop(value);
stu.showInformation();
/*
///
ClassName = class1.getSimpleName();
Sop(ClassName);
Sop("下面是获取特定函数");
Method[] ms = class1.getMethods();
for (Method m : ms) {
if (isGetter(m)) {
Sop("isGetter：" + m);
} else if (isSetter(m)) {
Sop("isSetter：" + m);
}
}
Sop("---");*/
}
private static boolean isSetter(Method m) {
// TODO Auto-generated method stub
if (!m.getName().startsWith("get"))
return false;
else if (m.getParameterTypes().length != 0)
return false;
else if (void.class.equals(m.getReturnType()))
return false;
return true;
}
private static boolean isGetter(Method m) {
// TODO Auto-generated method stub
if (!m.getName().startsWith("set"))
return false;
else if (m.getParameterTypes().length != 1)
return false;
return true;
}
private static void Sop(Object className) {
// TODO Auto-generated method stub
System.out.println(className);
}
}
五、Generics
六、 Dynamic Class Loading and Reloading