对象的克隆，Dozer的使用

Posted 2020-09-13 不想下火车的人

　　现在有个复杂对象bean需要在赋值后在另一个地方用，想通过复制的方式拿到这个对象。首选是深度克隆，虽然发现该对象的父类已经实现了Cloneable接口，但父类是通过jar包引入的，而且在clone方法中对该bean一个map<String, Object>属性的处理有问题：获取到map的value时，直接强制转型为某一具体bean，而子类这个map在put时并非该具体bean的类型，因此克隆时报转型失败错误。考虑方案二，通过java序列化方式克隆，父类也已经实现了Serializable接口，但写对象和度对象方法都是空实现，本地重新实现后也报错了。使用json序列化倒是可以，就是性能不高。最后决定采用Dozer框架，Dozer底层也是apache的beanUtils方式复制bean，但更易用，可以直接用xml文件或者注解映射两个类，类可以是不同类型，字段也可以是不同类型、不同名称。

　　使用前需要导入5个jar包：

commons-beanutils-1.9.3.jar

commons-lang3-3.5.jar

commons-logging-1.2.jar

dozer-5.4.0.jar

slf4j-api-1.7.25.jar

　　这里通过注解来实现一个例子，具体使用参见下面代码：

package com.wulinfeng.dozer;

import java.util.Date;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

public class CopyComponent {

    private String name;

    private int age;

    private Date date;

    private Map<String, String> internalMap;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public Date getDate() {
        return date;
    }

    public void setDate(Date date) {
        this.date = date;
    }

    public Map<String, String> getInternalMap() {
        return internalMap;
    }

    public void setInternalMap(Map<String, String> internalMap) {
        this.internalMap = internalMap;
    }

    @Override
    public String toString() {
        StringBuilder names = new StringBuilder();
        if (null != internalMap && internalMap.entrySet() != null) {
            Iterator<Entry<String, String>> iter = internalMap.entrySet().iterator();
            while (iter.hasNext()) {
                Entry<String, String> c = iter.next();
                names.append("key: ");
                names.append(c.getKey());
                names.append("value: ");
                names.append(c.getValue());
            }
        }
        return "name: " + name + ", age: " + age + ", date: " + date + ", list : " + names.toString();
    }

}

package com.wulinfeng.dozer;

import java.util.Date;
import java.util.HashMap;
import java.util.Map;

import org.dozer.DozerBeanMapper;
import org.dozer.Mapping;

public class Component {

    @Mapping("age")
    private String desc;

    @Mapping("name")
    private Integer price;

    private Date date;

    @Mapping("internalMap")
    private Map<String, String> externalAttrMap;

    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }

    public Integer getPrice() {
        return price;
    }

    public void setPrice(Integer price) {
        this.price = price;
    }

    public Date getDate() {
        return date;
    }

    public void setDate(Date date) {
        this.date = date;
    }

    public Map<String, String> getExternalAttrMap() {
        return externalAttrMap;
    }

    public void setExternalAttrMap(Map<String, String> externalAttrMap) {
        this.externalAttrMap = externalAttrMap;
    }

    public static void main(String[] args) {
        Component component = new Component();

        // String -> int
        component.setDesc("9999");

        // int -> String
        component.setPrice(30);

        // date -> date
        component.setDate(new Date());

        // Map -> List
        Component componentpage = new Component();
        componentpage.setDesc("hello");
        Map<String, String> ext = new HashMap<String, String>();
        ext.put("name", "fengjiangtao");
        component.setExternalAttrMap(ext);

        DozerBeanMapper dozerBeanMapper = new DozerBeanMapper();
        CopyComponent copy = dozerBeanMapper.map(component, CopyComponent.class);
        System.out.println(copy);
    }

}

　　运行结果：

SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
name: 30, age: 9999, date: Sun Apr 23 23:06:02 CST 2017, list : key: namevalue: fengjiangtao