反射效率为什么低?

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wx63ee08b3cead4 2023-02-20 00:48:04 博主文章分类：java基础 ©著作权

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反射效率为什么低

最近看spring源码相关内容，看到aop的实现，其中有动态代理涉及到反射内容，总有帖子说反射效率低，所以就想验证下反射效率是否整点低，以及低到什么程度？是否只要使用就很影响性能？

验证反射效率

代码

实体类

package org.springframework.test.reflect;

public class ReflectA {
  private int age;
  public String name;
  private String sex;

  public ReflectA(int age, String name, String sex) {
  
    this.age = age;
    this.name = name;
    this.sex = sex;
  }
  
  public int getAge() {
    return age;
  }
  
  public void setAge(int age) {
    this.age = age;
  }
  
  public String getName() {
    return name;
  }
  
  public void setName(String name) {
    this.name = name;
  }
  
  public String getSex() {
    return sex;
  }
  
  public void setSex(String sex) {
    this.sex = sex;
  }
}

测试类

package org.springframework.test.reflect;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

/**
 * 测试反射效率
 */
public class TestEfficiency {
  private static final int AVERAGE_COUNT = 10;
  private static final int executeCount = 1000;
  public static void main(String[] args) {
    long costTime = 0;
    long reflectMethodCostTime=0,normalMethodCostTime=0,reflectFieldCostTime=0,normalFieldCostTime=0;
    for(int index = 0; index < AVERAGE_COUNT; index++){

      costTime = getNormalCallCostTime(executeCount);
      reflectMethodCostTime += costTime;
  
      costTime = getReflectCallMethodCostTime(executeCount);
      normalMethodCostTime += costTime;
  
      costTime = getNormalFieldCostTime(executeCount);
      reflectFieldCostTime += costTime;
  
      costTime = getReflectCallFieldCostTime(executeCount);
      normalFieldCostTime += costTime;
    }
  
    System.out.println("reflectMethodCostTime: " + reflectMethodCostTime/AVERAGE_COUNT + " ms");
    System.out.println("normalMethodCostTime: " + normalMethodCostTime/AVERAGE_COUNT + " ms");
    System.out.println("reflectFieldCostTime: " + reflectFieldCostTime/AVERAGE_COUNT + " ms");
    System.out.println("normalFieldCostTime: " + normalFieldCostTime/AVERAGE_COUNT + " ms");
  }
  private static long getReflectCallMethodCostTime(int count){
    long startTime = System.currentTimeMillis();
    for(int index = 0 ; index < count; index++){
      ReflectA a = new ReflectA(12,"小明", "男");
      try{
        Method setName = a.getClass().getMethod("setName", String.class);
        setName.setAccessible(true);
        setName.invoke(a, "张三");
      }catch(IllegalAccessException e){
        e.printStackTrace();
      }catch(InvocationTargetException e){
        e.printStackTrace();
      }catch(NoSuchMethodException e){
        e.printStackTrace();
      }
    }

    return System.currentTimeMillis()-startTime;
  }

  private static long getReflectCallFieldCostTime(int count){
    long startTime = System.currentTimeMillis();
    for(int index = 0 ; index < count; index++){
      ReflectA a = new ReflectA(12,"小明", "男");
      try{
        Field ageField = a.getClass().getDeclaredField("name");
        ageField.set(a, "李四");
      }catch(NoSuchFieldException e){
        e.printStackTrace();
      }catch(IllegalAccessException e){
        e.printStackTrace();
      }
    }

    return System.currentTimeMillis()-startTime;
  }

  private static long getNormalCallCostTime(int count){
    long startTime = System.currentTimeMillis();
    for(int index = 0 ; index < count; index++){
      ReflectA a = new ReflectA(12,"小明", "男");
      a.setName("王五");
    }

    return System.currentTimeMillis()-startTime;
  }

  private static long getNormalFieldCostTime(int count){
    long startTime = System.currentTimeMillis();
    for(int index = 0 ; index < count; index++){
      ReflectA a = new ReflectA(12,"小明", "男");
      a.name = "候六";
    }

    return System.currentTimeMillis()-startTime;
  }
}