【Java面试进阶】谈一谈为什么禁止使用Apache BeanUtils进行属性的copy？

阳光穿透心脏的1/2处 2022-09-11 11:25 125阅读 0赞

### 谈一谈为什么禁止使用Apache BeanUtils进行属性的copy？ ###

*  业务背景
 *  性能比较

# 业务背景 #

日常开发中，我们经常需要给对象进行赋值，通常会调用其 set/get 方法，有些时候，如果要转换的两个对象之间属性大致相同，会考虑使用属性拷贝工具进行。

例如我们经常在代码中会对一个数据结构封装成 `DO`、`SDO`、`DTO`、`VO` 等，而这些 Bean 中的大部分属性都是一样的，所以使用属性拷贝类工具可以帮助我们节省大量的 set 和 get 操作。市面上有很多类似的工具类，比较常用的有

1.  Spring BeanUtils
2.  Cglib BeanCopier
3.  Apache BeanUtils
4.  Apache PropertyUtils
5.  Dozer

那么，到底应该选择哪种工具类更加合适呢？为什么 Java 开发手册中提到禁止使用 Apache BeanUtils 呢？其中给出的理由是：**Apache BeanUtils性能较差，可以使用其他方案比如Spring BeanUtils，Cglib BeanCopier，注意均是浅拷贝。**

# 性能比较 #

首先定义一个PersonDO类：

import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;
    
    import java.util.Date;
    
    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    public class PersonDO {
        
        private Integer id;
        private String name;
        private Integer age;
        private Date birthday;
        //省略setter/getter
    }

再定义一个PersonDTO类：

import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;
    
    import java.util.Date;
    
    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    public class PersonDTO {
        
        private String name;
        private Integer age;
        private Date birthday;
    }

然后进行测试类的编写：

import com.seckill.secondkill.DO.PersonDO;
    import com.seckill.secondkill.DTO.PersonDTO;
    import org.apache.commons.beanutils.PropertyUtils;
    import org.springframework.beans.BeanUtils;
    import org.springframework.cglib.beans.BeanCopier;
    import org.springframework.util.StopWatch;
    
    import java.lang.reflect.InvocationTargetException;
    import java.util.Date;
    
    /**
     * 对象属性拷贝工具
     * 1、Spring BeanUtils：效率其次
     * 2、Cglib BeanCopier：效率最高
     * 3、Apache BeanUtils：效率低,原因Apache BeanUtils力求做的完美，做了很多校验，兼容，日志打印等导致性能下降。
     * 4、Apache PropertyUtils：效率低
     * 5、Dozer
     * 使用场景：DO,DTO,VO,PO,BO等场景装换的时候通过对象属性拷贝提高开发效率，简化代码，
     * 但是同时也带来了隐藏拷贝了那些属性，没有直接转换更为直接，按需使用
     */
    public class MapperTest {
        
    
        public static void main(String[] args) throws InvocationTargetException, IllegalAccessException, NoSuchMethodException {
        
            PersonDO personDO = new PersonDO();
            personDO.setName("ZhangSan");
            personDO.setAge(26);
            personDO.setBirthday(new Date());
            personDO.setId(1);
    
            MapperTest mapperTest = new MapperTest();
            System.out.println("------mappingBySpringBeanUtils-------");
            mapperTest.mappingBySpringBeanUtils(personDO, 100);
            mapperTest.mappingBySpringBeanUtils(personDO, 1000);
            mapperTest.mappingBySpringBeanUtils(personDO, 10000);
            mapperTest.mappingBySpringBeanUtils(personDO, 100000);
            mapperTest.mappingBySpringBeanUtils(personDO, 1000000);
    
            System.out.println("------mappingByCglibBeanCopier-------");
            mapperTest.mappingByCglibBeanCopier(personDO, 100);
            mapperTest.mappingByCglibBeanCopier(personDO, 1000);
            mapperTest.mappingByCglibBeanCopier(personDO, 10000);
            mapperTest.mappingByCglibBeanCopier(personDO, 100000);
            mapperTest.mappingByCglibBeanCopier(personDO, 1000000);
    
            System.out.println("------mappingByApachePropertyUtils-------");
            mapperTest.mappingByApachePropertyUtils(personDO, 100);
            mapperTest.mappingByApachePropertyUtils(personDO, 1000);
            mapperTest.mappingByApachePropertyUtils(personDO, 10000);
            mapperTest.mappingByApachePropertyUtils(personDO, 100000);
            mapperTest.mappingByApachePropertyUtils(personDO, 1000000);
    
            System.out.println("------mappingByApacheBeanUtils-------");
            mapperTest.mappingByApacheBeanUtils(personDO, 100);
            mapperTest.mappingByApacheBeanUtils(personDO, 1000);
            mapperTest.mappingByApacheBeanUtils(personDO, 10000);
            mapperTest.mappingByApacheBeanUtils(personDO, 100000);
            mapperTest.mappingByApacheBeanUtils(personDO, 1000000);
        }
    
        // 使用Spring BeanUtils进行属性拷贝
        private void mappingBySpringBeanUtils(PersonDO personDO, int times) {
        
            StopWatch stopwatch = new StopWatch();
            stopwatch.start();
    
            for (int i = 0; i < times; i++) {
        
                PersonDTO personDTO = new PersonDTO();
                org.springframework.beans.BeanUtils.copyProperties(personDO, personDTO);
            }
    
            stopwatch.stop();
            System.out.println("mappingBySpringBeanUtils cost :" + stopwatch.getTotalTimeMillis());
        }
    
        // 使用Cglib BeanCopier进行属性拷贝
        private void mappingByCglibBeanCopier(PersonDO personDO, int times) {
        
            StopWatch stopwatch = new StopWatch();
            stopwatch.start();
            for (int i = 0; i < times; i++) {
        
                PersonDTO personDTO = new PersonDTO();
                BeanCopier copier = BeanCopier.create(PersonDO.class, PersonDTO.class, false);
                copier.copy(personDO, personDTO, null);
            }
            stopwatch.stop();
            System.out.println("mappingByCglibBeanCopier cost :" + stopwatch.getTotalTimeMillis());
        }
    
        // 使用Apache BeanUtils进行属性拷贝
        private void mappingByApacheBeanUtils(PersonDO personDO, int times)
                throws InvocationTargetException, IllegalAccessException {
        
            StopWatch stopwatch = new StopWatch();
            stopwatch.start();
            for (int i = 0; i < times; i++) {
        
                PersonDTO personDTO = new PersonDTO();
                BeanUtils.copyProperties(personDTO, personDO);
            }
            stopwatch.stop();
            System.out.println("mappingByApacheBeanUtils cost :" + stopwatch.getTotalTimeMillis());
        }
    
        // 使用Apache PropertyUtils进行属性拷贝
        private void mappingByApachePropertyUtils(PersonDO personDO, int times)
                throws InvocationTargetException, IllegalAccessException, NoSuchMethodException {
        
            StopWatch stopwatch = new StopWatch();
            stopwatch.start();
            for (int i = 0; i < times; i++) {
        
                PersonDTO personDTO = new PersonDTO();
                PropertyUtils.copyProperties(personDTO, personDO);
            }
            stopwatch.stop();
            System.out.println("mappingByApachePropertyUtils cost :" + stopwatch.getTotalTimeMillis());
        }
    }

其中的StopWatch用于记录代码执行时间，方便进行对比。

然而执行报错：

mappingBySpringBeanUtils cost :102
    mappingBySpringBeanUtils cost :3
    mappingBySpringBeanUtils cost :20
    mappingBySpringBeanUtils cost :31
    mappingBySpringBeanUtils cost :137
    ------mappingByCglibBeanCopier-------
    Exception in thread "main" java.lang.NullPointerException: Cannot invoke "Object.getClass()" because "cause" is null
    	at org.springframework.cglib.core.CodeGenerationException.<init>(CodeGenerationException.java:25)
    	at org.springframework.cglib.core.ReflectUtils.defineClass(ReflectUtils.java:567)
    	at org.springframework.cglib.core.AbstractClassGenerator.generate(AbstractClassGenerator.java:363)
    	at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:110)
    	at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:108)
    	at org.springframework.cglib.core.internal.LoadingCache$2.call(LoadingCache.java:54)
    	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    	at org.springframework.cglib.core.internal.LoadingCache.createEntry(LoadingCache.java:61)
    	at org.springframework.cglib.core.internal.LoadingCache.get(LoadingCache.java:34)
    	at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData.get(AbstractClassGenerator.java:134)
    	at org.springframework.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:319)
    	at org.springframework.cglib.beans.BeanCopier$Generator.create(BeanCopier.java:95)
    	at org.springframework.cglib.beans.BeanCopier.create(BeanCopier.java:51)
    	at com.seckill.secondkill.utils.MapperTest.mappingByCglibBeanCopier(MapperTest.java:82)
    	at com.seckill.secondkill.utils.MapperTest.main(MapperTest.java:41)

--------------------

下面内容直接抄袭：

<table> 
 <thead> 
  <tr> 
   <th align="center">工具类</th> 
   <th align="right">执行1000次耗时</th> 
   <th>执行10000次耗时</th> 
   <th>执行100000次耗时</th> 
   <th>执行1000000次耗时</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="center">Spring BeanUtils</td> 
   <td align="right">5ms</td> 
   <td>10ms</td> 
   <td>45ms</td> 
   <td>169ms</td> 
  </tr> 
  <tr> 
   <td align="center">Cglib BeanCopier</td> 
   <td align="right">4ms</td> 
   <td>18ms</td> 
   <td>45ms</td> 
   <td>91ms</td> 
  </tr> 
  <tr> 
   <td align="center">Apache PropertyUtils</td> 
   <td align="right">60ms</td> 
   <td>265ms</td> 
   <td>1444ms</td> 
   <td>11492ms</td> 
  </tr> 
  <tr> 
   <td align="center">Apache BeanUtils</td> 
   <td align="right">138ms</td> 
   <td>816ms</td> 
   <td>4154ms</td> 
   <td>36938ms</td> 
  </tr> 
  <tr> 
   <td align="center">Dozer</td> 
   <td align="right">566ms</td> 
   <td>2254ms</td> 
   <td>11136ms</td> 
   <td>102965ms</td> 
  </tr> 
 </tbody> 
</table>

![性能比对图][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA6ZWw5YiA6Z-t6I-c_size_20_color_FFFFFF_t_70_g_se_x_16]  
综上，在性能方面，Spring BeanUtils和Cglib BeanCopier表现比较不错，而Apache PropertyUtils、Apache BeanUtils以及Dozer表现则很不好。  
所以，如果考虑性能情况，不要使用Apache PropertyUtils、Apache BeanUtils以及Dozer等工具类。

[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA6ZWw5YiA6Z-t6I-c_size_20_color_FFFFFF_t_70_g_se_x_16]: /images/20220828/1382023510154d89a6d4d053170cfb88.png