反射setaccessible_反射技术

package com.sxt.fanshe;import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Arrays;public class TestClass {public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException, SecurityException {//(1)获取类的名称Class forName = Class.forName("com.sxt.entity.User");//2.类名.class//Class calzz = User.class;//3.对象名.getClass()//User user = new User();//Class clazz = user.getClass();System.out.println("类的全名称："+forName.getName());//获取包名+类名System.out.println("类的名称："+forName.getSimpleName());//获取类名//获取父类的System.out.println("父类的全名称："+forName.getSuperclass().getName());System.out.println("父类的名称："+forName.getSuperclass().getSimpleName());System.out.println("-------------------------------------");//(2)获取类的属性System.out.println("获取类的属性：");Field field = forName.getField("username");System.out.println(field);//只能获取公共的属性Field[] fields = forName.getFields();//只能获取所有公共属性System.out.println("公共属性值共有："+fields.length);for (Field field2 : fields) {System.out.println(field2);}//获取所有属性值System.out.println("获取所有属性值:");Field[] field3 = forName.getDeclaredFields();System.out.println("属性值共有："+field3.length);for (Field field4 : field3) {System.out.println(field4);}System.out.println("-------------------------------------");//获取方法值Method[] getDeclaredMethods() 得到公共的方法对象System.out.println("得到公共的方法对象:");Method[] methods = forName.getDeclaredMethods();for (Method method : methods) {System.out.println(method);}System.out.println("-------------------------------------");System.out.println("得到父类的方法对象:");Method[] methods2 = forName.getMethods();for (Method method : methods2) {System.out.println(method);}System.out.println("-------------------------------------");//获取构造器System.out.println("获取构造器");Constructor[] constructors = forName.getConstructors();for (Constructor constructor : constructors) {Class[] parameterTypes = constructor.getParameterTypes();//获取参数类型int cMod = constructor.getModifiers();//获取构造器修饰符String name = forName.getName();//获取名字System.out.println(cMod+"---"+name+"---"+Arrays.toString(parameterTypes));System.out.println(constructor);}}
}

package com.sxt.fanshe;import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;/*** 	提高效率setAccessible(true);禁用安全检查，可以提高运行速度* @date 2019年8月8日*/
public class Test3 {public static void test01(){Object obj = new Object();long startTime = System.currentTimeMillis();//设置开始时间for (int i = 0; i < 1000000000; i++) {obj.hashCode();}long endTime = System.currentTimeMillis();//设置结束时间System.out.println("调用普通方法执行10亿次时间："+(endTime-startTime)+"ms");}public static void test02() throws Exception{Object obj = new Object();Class clazz = obj.getClass();//获取hashcode方法Method method = clazz.getDeclaredMethod("hashCode", null);long startTime = System.currentTimeMillis();//设置开始时间for (int i = 0; i < 1000000000; i++) {
//			obj.hashCode();method.invoke(obj);}long endTime = System.currentTimeMillis();//设置结束时间System.out.println("调用反射回调方法执行10亿次时间："+(endTime-startTime)+"ms");}public static void test03() throws Exception{Object obj = new Object();Class clazz = obj.getClass();//获取hashcode方法Method method = clazz.getDeclaredMethod("hashCode", null);method.setAccessible(true);//设置是否取消安全检查long startTime = System.currentTimeMillis();//设置开始时间for (int i = 0; i < 1000000000; i++) {
//			obj.hashCode();method.invoke(obj);}long endTime = System.currentTimeMillis();//设置结束时间System.out.println("调用优化后反射回调方法执行10亿次时间："+(endTime-startTime)+"ms");}public static void main(String[] args) throws Exception {test01();test02();test03();}
}

package com.sxt.fanshe;import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.List;
import java.util.Map;import com.sxt.entity.User;public class TestGeneric {public void test01(Map<String,User> map,List<User> list,String s){System.out.println("TestGeneric.test01()");}public Map<Integer,User> test02(){System.out.println("TestGeneric.test02()");return null;}public String test03(){System.out.println("TestGeneric.test03()");return null;}public static void main(String[] args) throws NoSuchMethodException, SecurityException {//获取test01方法的泛型参数信息Class c=TestGeneric.class;Method test01=c.getMethod("test01", Map.class,List.class,String.class);//获取带泛型参数的类型Type [] tytes=test01.getGenericParameterTypes();System.out.println(tytes.length);for (Type type : tytes) {//System.out.println("#"+type);if (type instanceof ParameterizedType) {Type[] genericType= ((ParameterizedType) type).getActualTypeArguments();//遍历每一个泛型参数中泛型的类型  for (Type genType : genericType) {System.out.println("泛型类型:"+genType);}System.out.println("n--------------------------");}}System.out.println("n----------------------------n");//获取test02方法返回值的泛型信息Method m2=c.getMethod("test02", null);Type returnType=m2.getGenericReturnType();//判断是否带有泛型if(returnType instanceof ParameterizedType){Type [] types=((ParameterizedType) returnType).getActualTypeArguments();for (Type type : types) {System.out.println("返回值的泛型类型:"+type);}}System.out.println("n------------------------------n");Method m3=c.getMethod("test03", null);Type returnType3=m3.getGenericReturnType();//System.out.println(returnType3);System.out.println(returnType3 instanceof ParameterizedType);}}