常见Bean拷贝框架使用姿势及性能对比

Bean属性拷贝，主要针对几个常用的拷贝框架进行性能对比，以及功能扩展支持

选用的框架

• cglib (直接使用Spring封装的BeanCopier)
• apache
• MapStruct
• Spring
• HuTool

I.背景

当业务量不大时，不管选择哪个框架都没什么问题，只要功能支持就ok了；但是当数据量大的时候，可能就需要考虑性能问题了；再实际的项目中，正好遇到了这个问题，不仅慢，还发现会有锁竞争，这特么就尼普了

项目中使用的是Spring的 BeanUtils， 版本 3.2.4.RELEASE， 版本相对较老，主要问题在于org.springframework.beans.CachedIntrospectionResults.forClass

/**
 * Create CachedIntrospectionResults for the given bean class.
 * <P>We don't want to use synchronization here. Object references are atomic,
 * so we can live with doing the occasional unnecessary lookup at startup only.
 * @param beanClass the bean class to analyze
 * @return the corresponding CachedIntrospectionResults
 * @throws BeansException in case of introspection failure
 */
static CachedIntrospectionResults forClass(Class beanClass) throws BeansException {
    CachedIntrospectionResults results;
    Object value;
    synchronized (classCache) {
        value = classCache.get(beanClass);
    }
    if (value instanceof Reference) {
        Reference ref = (Reference) value;
        results = (CachedIntrospectionResults) ref.get();
    }
    else {
        results = (CachedIntrospectionResults) value;
    }
    if (results == null) {
        if (ClassUtils.isCacheSafe(beanClass, CachedIntrospectionResults.class.getClassLoader()) ||
                isClassLoaderAccepted(beanClass.getClassLoader())) {
            results = new CachedIntrospectionResults(beanClass);
            synchronized (classCache) {
                classCache.put(beanClass, results);
            }
        }
        else {
            if (logger.isDebugEnabled()) {
                logger.debug("Not strongly caching class [" + beanClass.getName() + "] because it is not cache-safe");
            }
            results = new CachedIntrospectionResults(beanClass);
            synchronized (classCache) {
                classCache.put(beanClass, new WeakReference<CachedIntrospectionResults>(results));
            }
        }
    }
    return results;
}

看上面的实现，每次获取value都加了一个同步锁，而且还是锁的全局的classCache，这就有些过分了啊，微妙的是这段代码注释，谷歌翻译之后为

我们不想在这里使用同步。 对象引用是原子的，因此我们可以只在启动时进行偶尔的不必要查找。

这意思大概是说我就在启动的时候用一下，并不会频繁的使用，所以使用了同步代码块也问题不大...

但是在BeanUtils#copyProperties中就蛋疼了，每次都会执行这个方法，扎心了

当然我们现在一般用的Spring5+了，这段代码也早就做了改造了，新版的如下，不再存在上面的这个并发问题了

/**
 * Create CachedIntrospectionResults for the given bean class.
 * @param beanClass the bean class to analyze
 * @return the corresponding CachedIntrospectionResults
 * @throws BeansException in case of introspection failure
 */
@SuppressWarnings("unchecked")
static CachedIntrospectionResults forClass(Class<?> beanClass) throws BeansException {
    CachedIntrospectionResults results = strongClassCache.get(beanClass);
    if (results != null) {
        return results;
    }
    results = softClassCache.get(beanClass);
    if (results != null) {
        return results;
    }

    results = new CachedIntrospectionResults(beanClass);
    ConcurrentMap<Class<?>, CachedIntrospectionResults> classCacheToUse;

    if (ClassUtils.isCacheSafe(beanClass, CachedIntrospectionResults.class.getClassLoader()) ||
            isClassLoaderAccepted(beanClass.getClassLoader())) {
        classCacheToUse = strongClassCache;
    }
    else {
        if (logger.isDebugEnabled()) {
            logger.debug("Not strongly caching class [" + beanClass.getName() + "] because it is not cache-safe");
        }
        classCacheToUse = softClassCache;
    }

    CachedIntrospectionResults existing = classCacheToUse.putIfAbsent(beanClass, results);
    return (existing != null ? existing : results);
}

II. 不同框架使用姿势

接下来我们看一下几种常见的bean拷贝框架的使用姿势，以及对比测试

1. apache BeanUtils

阿里规范中，明确说明了，不要使用它，idea安装阿里的代码规范插件之后，会有提示

使用姿势比较简单，引入依赖

<!-- https://mvnrepository.com/artifact/commons-beanutils/commons-beanutils -->
<dependency>
    <groupId>commons-beanutils</groupId>
    <artifactId>commons-beanutils</artifactId>
    <version>1.9.4</version>
</dependency>

属性拷贝

@Component
public class ApacheCopier {
    public <K, T> T copy(K source, Class<T> target) throws IllegalAccessException, InstantiationException, InvocationTargetException {
        T res = target.newInstance();
        // 注意，第一个参数为target，第二个参数为source
        // 与其他的正好相反 
        BeanUtils.copyProperties(res, source);
        return res;
    }
}

2. cglib BeanCopier

cglib是通过动态代理的方式来实现属性拷贝的，与上面基于反射实现方式存在本质上的区别，这也是它性能更优秀的主因

在Spring环境下，一般不需要额外的引入依赖；或者直接引入spring-core

<!--      cglib  -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-core</artifactId>
    <version>5.2.8.RELEASE</version>
    <scope>compile</scope>
</dependency>

属性拷贝

@Component
public class SpringCglibCopier {
    /**
     * cglib 对象转换
     *
     * @param source
     * @param target
     * @param <K>
     * @param <T>
     * @return
     * @throws IllegalAccessException
     * @throws InstantiationException
     */
    public <K, T> T copy(K source, Class<T> target) throws IllegalAccessException, InstantiationException {
        BeanCopier copier = BeanCopier.create(source.getClass(), target, false);
        T res = target.newInstance();
        copier.copy(source, res, null);
        return res;
    }
}

当然也可以直接使用纯净版的cglib，引入依赖

<dependency>
    <groupId>cglib</groupId>
    <artifactId>cglib</artifactId>
    <version>3.3.0</version>
</dependency>

使用姿势和上面一模一样

@Component
public class PureCglibCopier {
    /**
     * cglib 对象转换
     *
     * @param source
     * @param target
     * @param <K>
     * @param <T>
     * @return
     * @throws IllegalAccessException
     * @throws InstantiationException
     */
    public <K, T> T copy(K source, Class<T> target) throws IllegalAccessException, InstantiationException {
        BeanCopier copier = BeanCopier.create(source.getClass(), target, false);
        T res = target.newInstance();
        copier.copy(source, res, null);
        return res;
    }
}

3. spring BeanUtils

这里使用的是spring 5.2.1.RELEASE， 就不要拿3.2来使用了，不然并发下的性能实在是感人

基于内省+反射，借助getter/setter方法实现属性拷贝，性能比apache高

核心依赖

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-beans</artifactId>
    <version>5.2.1.RELEASE</version>
    <scope>compile</scope>
</dependency>

属性拷贝

@Component
public class SpringBeanCopier {

    /**
     * 对象转换
     *
     * @param source
     * @param target
     * @param <K>
     * @param <T>
     * @return
     * @throws IllegalAccessException
     * @throws InstantiationException
     */
    public <K, T> T copy(K source, Class<T> target) throws IllegalAccessException, InstantiationException {
        T res = target.newInstance();
        BeanUtils.copyProperties(source, res);
        return res;
    }
}

4. hutool BeanUtil

hutool 提供了很多的java工具类，从测试效果来看它的性能比apache会高一点，当低于spring

引入依赖

<dependency>
    <groupId>cn.hutool</groupId>
    <artifactId>hutool-core</artifactId>
    <version>5.6.0</version>
</dependency>

使用姿势

@Component
public class HutoolCopier {

    /**
     * bean 对象转换
     *
     * @param source
     * @param target
     * @param <K>
     * @param <T>
     * @return
     */
    public <K, T> T copy(K source, Class<T> target) throws Exception {
        return BeanUtil.toBean(source, target);
    }
}

5. MapStruct

MapStruct 性能更强悍了，缺点也比较明显，需要声明bean的转换接口，自动代码生成的方式来实现拷贝，性能媲美直接的get/set

引入依赖

<dependency>
    <groupId>org.mapstruct</groupId>
    <artifactId>mapstruct</artifactId>
    <version>1.4.2.Final</version>
</dependency>
<dependency>
    <groupId>org.mapstruct</groupId>
    <artifactId>mapstruct-processor</artifactId>
    <version>1.4.2.Final</version>
</dependency>

使用姿势

@Mapper
public interface MapStructCopier {
    Target copy(Source source);
}

@Component
public class MapsCopier {
    private MapStructCopier mapStructCopier = Mappers.getMapper(MapStructCopier.class);

    public Target copy(Source source, Class<Target> target) {
        return mapStructCopier.copy(source);
    }
}

缺点也比较明显，需要显示的接口转换声明

6. 测试

定义两个Bean，用于转换测试，两个bean的成员属性名，类型完全一致

@Data
public class Source {
    private Integer id;
    private String user_name;
    private Double price;
    private List<Long> ids;
    private BigDecimal marketPrice;
}

@Data
public class Target {
    private Integer id;
    private String user_name;
    private Double price;
    private List<Long> ids;
    private BigDecimal marketPrice;
}

6.1 功能测试

private Random random = new Random();

public Source genSource() {
    Source source = new Source();
    source.setId(random.nextInt());
    source.setIds(Arrays.asList(random.nextLong(), random.nextLong(), random.nextLong()));
    source.setMarketPrice(new BigDecimal(random.nextFloat()));
    source.setPrice(random.nextInt(120) / 10.0d);
    source.setUser_name("一灰灰Blog");
    return source;
}


 private void copyTest() throws Exception {
        Source s = genSource();
        Target ta = apacheCopier.copy(s, Target.class);
        Target ts = springBeanCopier.copy(s, Target.class);
        Target tc = springCglibCopier.copy(s, Target.class);
        Target tp = pureCglibCopier.copy(s, Target.class);
        Target th = hutoolCopier.copy(s, Target.class);
        Target tm = mapsCopier.copy(s, Target.class);
        System.out.println("source:\t" + s + "\napache:\t" + ta + "\nspring:\t" + ts
                + "\nsCglib:\t" + tc + "\npCglib:\t" + tp + "\nhuTool:\t" + th + "\nmapStruct:\t" + tm);
}

输出结果如下，满足预期

source: Source(id=1337715455, user_name=一灰灰Blog, price=7.1, ids=[7283949433132389385, 3441022909341384204, 8273318310870260875], marketPrice=0.04279220104217529296875)
apache: Target(id=1337715455, user_name=一灰灰Blog, price=7.1, ids=[7283949433132389385, 3441022909341384204, 8273318310870260875], marketPrice=0.04279220104217529296875)
spring: Target(id=1337715455, user_name=一灰灰Blog, price=7.1, ids=[7283949433132389385, 3441022909341384204, 8273318310870260875], marketPrice=0.04279220104217529296875)
sCglib: Target(id=1337715455, user_name=一灰灰Blog, price=7.1, ids=[7283949433132389385, 3441022909341384204, 8273318310870260875], marketPrice=0.04279220104217529296875)
pCglib: Target(id=1337715455, user_name=一灰灰Blog, price=7.1, ids=[7283949433132389385, 3441022909341384204, 8273318310870260875], marketPrice=0.04279220104217529296875)
huTool: Target(id=1337715455, user_name=一灰灰Blog, price=7.1, ids=[7283949433132389385, 3441022909341384204, 8273318310870260875], marketPrice=0.04279220104217529296875)
mapStruct:  Target(id=1337715455, user_name=一灰灰Blog, price=7.1, ids=[7283949433132389385, 3441022909341384204, 8273318310870260875], marketPrice=0.04279220104217529296875)

6.2 性能测试

接下来我们关注一下不同的工具包，实现属性拷贝的性能对比情况如何

public void test() throws Exception {
    // 第一次用于预热
    autoCheck(Target2.class, 10000);
    autoCheck(Target2.class, 10000);
    autoCheck(Target2.class, 10000_0);
    autoCheck(Target2.class, 50000_0);
    autoCheck(Target2.class, 10000_00);
}

private <T> void autoCheck(Class<T> target, int size) throws Exception {
    StopWatch stopWatch = new StopWatch();
    runCopier(stopWatch, "apacheCopier", size, (s) -> apacheCopier.copy(s, target));
    runCopier(stopWatch, "springCglibCopier", size, (s) -> springCglibCopier.copy(s, target));
    runCopier(stopWatch, "pureCglibCopier", size, (s) -> pureCglibCopier.copy(s, target));
    runCopier(stopWatch, "hutoolCopier", size, (s) -> hutoolCopier.copy(s, target));
    runCopier(stopWatch, "springBeanCopier", size, (s) -> springBeanCopier.copy(s, target));
    runCopier(stopWatch, "mapStruct", size, (s) -> mapsCopier.copy(s, target));
    System.out.println((size / 10000) + "w -------- cost: " + stopWatch.prettyPrint());
}

private <T> void runCopier(StopWatch stopWatch, String key, int size, CopierFunc func) throws Exception {
    stopWatch.start(key);
    for (int i = 0; i < size; i++) {
        Source s = genSource();
        func.apply(s);
    }
    stopWatch.stop();
}

@FunctionalInterface
public interface CopierFunc<T> {
    T apply(Source s) throws Exception;
}

输出结果如下

1w -------- cost: StopWatch '': running time = 583135900 ns
---------------------------------------------
ns         %     Task name
---------------------------------------------
488136600  084%  apacheCopier
009363500  002%  springCglibCopier
009385500  002%  pureCglibCopier
053982900  009%  hutoolCopier
016976500  003%  springBeanCopier
005290900  001%  mapStruct

10w -------- cost: StopWatch '': running time = 5607831900 ns
---------------------------------------------
ns         %     Task name
---------------------------------------------
4646282100  083%  apacheCopier
096047200  002%  springCglibCopier
093815600  002%  pureCglibCopier
548897800  010%  hutoolCopier
169937400  003%  springBeanCopier
052851800  001%  mapStruct

50w -------- cost: StopWatch '': running time = 27946743000 ns
---------------------------------------------
ns         %     Task name
---------------------------------------------
23115325200  083%  apacheCopier
481878600  002%  springCglibCopier
475181600  002%  pureCglibCopier
2750257900  010%  hutoolCopier
855448400  003%  springBeanCopier
268651300  001%  mapStruct

100w -------- cost: StopWatch '': running time = 57141483600 ns
---------------------------------------------
ns         %     Task name
---------------------------------------------
46865332600  082%  apacheCopier
1019163600  002%  springCglibCopier
1033701100  002%  pureCglibCopier
5897726100  010%  hutoolCopier
1706155900  003%  springBeanCopier
619404300  001%  mapStruct

上面的测试中，存在一个不同的变量，即不是用相同的source对象来测试不同的工具转换情况，但是这个不同并不会太影响不同框架的性能对比，基本上从上面的运行结果来看

• mapstruct, cglib, spring 表现最好
• apache 表现最差

基本趋势相当于:

apache -> 10 * hutool -> 28 * spring -> 45 * cglib -> 83 * mapstruct

如果我们需要实现简单的bean拷贝，选择cglib或者spring的是个不错选择

III. 其他

1. 一灰灰Blog： https://blog.hhui.top

一灰灰的个人博客，记录所有学习和工作中的博文，欢迎大家前去逛逛

• 项目源码: https://github.com/liuyueyi/spring-boot-demo/tree/master/spring-boot/004-bean-util

2. 声明

尽信书则不如，以上内容，纯属一家之言，因个人能力有限，难免有疏漏和错误之处，如发现bug或者有更好的建议，欢迎批评指正，不吝感激

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