拷贝简单对象的四种方法及性能分析

前言

本文转自美女程序媛,她的博客原文地址:  https://blog.csdn.net/duagh7/article/details/80857463

实际项目中，我们常常需要对对象进行拷贝，此文将列出四种常见的对象拷贝方式，并针对它们分别做出实验进行性能分析。

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此次实验用于拷贝的简单对象如下：

class CurrencyDailyBo implements Serializable {
    private static final long serialVersionUID = 1L;
    private int id;
    private Date day;
    private double amountMoney;
    private int businessNum;
    private int balanceNum;
    private Integer type;
    private String createTime;
    private String modifyTime ;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public Date getDay() {
        return day;
    }
    public void setDay(Date day) {
        this.day = day;
    }
    public double getAmountMoney() {
        return amountMoney;
    }
    public void setAmountMoney(double amountMoney) {
        this.amountMoney = amountMoney;
    }
    public int getBusinessNum() {
        return businessNum;
    }
    public void setBusinessNum(int businessNum) {
        this.businessNum = businessNum;
    }
    public int getBalanceNum() {
        return balanceNum;
    }
    public void setBalanceNum(int balanceNum) {
        this.balanceNum = balanceNum;
    }
    public String getCreateTime() {
        return createTime;
    }
    public void setCreateTime(String createTime) {
        this.createTime = createTime;
    }
    public Integer getType() {
        return type;
    }
    public void setType(Integer type) {
        this.type = type;
    }
    public String getModifyTime() {
        return modifyTime;
    }
    public void setModifyTime(String modifyTime) {
        this.modifyTime = modifyTime;
    }
    @Override
    public String toString() {
        return JSON.toJSONString(this);
    }
}

 

方法一、get / set方法

最原始拷贝对象的方法，new一个新对象，然后进行get，set方法拷贝属性，代码如下：

@Test
    public void getset() {
        CurrencyDailyBo currencyDailyBo = new CurrencyDailyBo();
        currencyDailyBo.setAmountMoney(111);
        currencyDailyBo.setBalanceNum(1);
        currencyDailyBo.setBusinessNum(2);
        currencyDailyBo.setCreateTime("today");
        currencyDailyBo.setModifyTime("today");
        currencyDailyBo.setDay(new Date());
        currencyDailyBo.setId(1111111);
        currencyDailyBo.setType(1);
        long start = System.currentTimeMillis();
        for (int i = 0; i < 100000; i++) {
            CurrencyDailyBo copyBo = new CurrencyDailyBo();
            copyBo.setType(currencyDailyBo.getType());
            copyBo.setId(currencyDailyBo.getId());
            copyBo.setDay(currencyDailyBo.getDay());
            copyBo.setAmountMoney(currencyDailyBo.getAmountMoney());
            copyBo.setBalanceNum(currencyDailyBo.getBalanceNum());
            copyBo.setBusinessNum(currencyDailyBo.getBusinessNum());
            copyBo.setCreateTime(currencyDailyBo.getCreateTime());
            copyBo.setModifyTime(currencyDailyBo.getModifyTime());
        }
        long cost = System.currentTimeMillis() - start;
        System.out.println("get，set方法拷贝10万个简单对象，耗时====" + cost);
    }

运行结果：

get，set方法拷贝10万个简单对象，耗时====15

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方法二、beanutils工具类拷贝

第二种方法我们使用apache提供的工具类（spring也提供了类似的工具类）beanutils.copyProperties来进行拷贝，其底层实现原理为反射，代码如下：

@Test
    public void beanutilsForCopy() throws InvocationTargetException, IllegalAccessException {
        CurrencyDailyBo currencyDailyBo = new CurrencyDailyBo();
        currencyDailyBo.setAmountMoney(111);
        currencyDailyBo.setBalanceNum(1);
        currencyDailyBo.setBusinessNum(2);
        currencyDailyBo.setCreateTime("today");
        currencyDailyBo.setModifyTime("today");
        currencyDailyBo.setDay(new Date());
        currencyDailyBo.setId(1111111);
        currencyDailyBo.setType(1);
        long start = System.currentTimeMillis();
        for (int i = 0; i < 100000; i++) {
            CurrencyDailyBo copyBo = new CurrencyDailyBo();
            BeanUtils.copyProperties(copyBo, currencyDailyBo);
        }
        long cost = System.currentTimeMillis() - start;
        System.out.println("beanutils工具类拷贝10万个简单对象，耗时====" + cost);
    }

运行结果：

beanutils工具类拷贝10万个简单对象，耗时====3495

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方法三、通过json字符串转入转出

第三种方法我们通过fastjson将对象转入json字符串，再使用parseObject转出为对象，代码如下：

@Test
    public void jsonForCopy() {
        CurrencyDailyBo currencyDailyBo = new CurrencyDailyBo();
        currencyDailyBo.setAmountMoney(111);
        currencyDailyBo.setBalanceNum(1);
        currencyDailyBo.setBusinessNum(2);
        currencyDailyBo.setCreateTime("today");
        currencyDailyBo.setModifyTime("today");
        currencyDailyBo.setDay(new Date());
        currencyDailyBo.setId(1111111);
        currencyDailyBo.setType(1);
        long start = System.currentTimeMillis();
        for (int i = 0; i < 100000; i++) {
            String json = JSON.toJSONString(currencyDailyBo);
            CurrencyDailyBo copyBo = JSON.parseObject(json, CurrencyDailyBo.class);
        }
        long cost = System.currentTimeMillis() - start;
        System.out.println("jsonString拷贝10万个简单对象，耗时====" + cost);
    }

运行结果：

jsonString拷贝10万个简单对象，耗时====374

此方法还可用于原被拷贝对象为map集合的情况。

 

 

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方法四、重写clone方法

这种方法在实际项目中较少使用，它是通过实现cloneable接口及重写clone方法来拷贝对象，但它的效率是最高的，有条件的情况下可以使用该方法。对于复杂对象（嵌套、链表等）来说，必须对其子对象也实现clone方法，否则拷贝结果会丢失子对象的属性数据，代码如下：

    @Test
    public void cloneForCopy() {
        CurrencyDailyBo currencyDailyBo = new CurrencyDailyBo();
        currencyDailyBo.setAmountMoney(111);
        currencyDailyBo.setBalanceNum(1);
        currencyDailyBo.setBusinessNum(2);
        currencyDailyBo.setCreateTime("today");
        currencyDailyBo.setModifyTime("today");
        currencyDailyBo.setDay(new Date());
        currencyDailyBo.setId(1111111);
        currencyDailyBo.setType(1);
        long start = System.currentTimeMillis();
        for (int i = 0; i < 100000; i++) {
            Object copyBo = currencyDailyBo.clone();
        }
        long cost = System.currentTimeMillis() - start;
        System.out.println("clone方法拷贝10万个简单对象，耗时====" + cost);
    }

重写对象：

class CurrencyDailyBo implements Serializable ,Cloneable{
    private static final long serialVersionUID = 1L;
    private int id;
    private Date day;
    private double amountMoney;
    private int businessNum;
    private int balanceNum;
    private Integer type;
    private String createTime;
    private String modifyTime;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public Date getDay() {
        return day;
    }
    public void setDay(Date day) {
        this.day = day;
    }
    public double getAmountMoney() {
        return amountMoney;
    }
    public void setAmountMoney(double amountMoney) {
        this.amountMoney = amountMoney;
    }
    public int getBusinessNum() {
        return businessNum;
    }
    public void setBusinessNum(int businessNum) {
        this.businessNum = businessNum;
    }
    public int getBalanceNum() {
        return balanceNum;
    }
    public void setBalanceNum(int balanceNum) {
        this.balanceNum = balanceNum;
    }
    public String getCreateTime() {
        return createTime;
    }
    public void setCreateTime(String createTime) {
        this.createTime = createTime;
    }
    public Integer getType() {
        return type;
    }
    public void setType(Integer type) {
        this.type = type;
    }
    public String getModifyTime() {
        return modifyTime;
    }
    public void setModifyTime(String modifyTime) {
        this.modifyTime = modifyTime;
    }
    @Override
    public String toString() {
        return JSON.toJSONString(this);
    }
    @Override
    public Object clone() {
        try {
            return super.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        return null;
    }
}

运行结果：

clone方法拷贝10万个简单对象，耗时====0

 

四、总结

通过以上测试，我们可以发现传统的get、set方法，复制10万个基本对象耗时15毫秒，以此为标准，jsonstring方式耗时大约稳定在getset方法的20倍左右。再次是beanutils方法，耗时基本稳定在getset方法的200倍左右，此方法不建议使用，因为它的功能使用json可以完全代替，而它的耗时最长。最后，重写clone方法来拷贝对象效率是最高的，但实现不易，复杂对象的拷贝需使所有子对象都实现clone方法，实际项目中较少使用。

以上是拷贝简单对象的四种方法及各自性能分析。