Java:通过反射复制父类字段到子类。

有些时候需要建立子类继承于父类，尤其是java里面很多类是用mybatis generator生成的。通过父类构造子类，好像很麻烦，要逐个字段进行赋值（反正我没有找到其他好办法）。

想到用反射复制的方式来实现。通过研究，做到了。主要是用了fastjson里面的东西。估计已经有其他类库实现了这个功能，可惜我不知道，只能自己搞。

　　

import java.beans.Statement;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Type;
import java.util.List;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.util.DeserializeBeanInfo;
import com.alibaba.fastjson.util.FieldInfo;
import com.alibaba.fastjson.util.TypeUtils;

/**
 * Created by fenggqc on 2016/6/29.
 */
public class Copyer {


    public static <B, S extends B>  void Copy(B bo, S so) throws IllegalAccessException {

        try {
            Class bc = bo.getClass();
            if (bo == null || so == null) {
                return;
            }


            DeserializeBeanInfo deserializeBeanInfo = DeserializeBeanInfo.computeSetters(so.getClass(), (Type) so.getClass());
            List<FieldInfo> getters = TypeUtils.computeGetters(bo.getClass(), null);

            List<FieldInfo> setters = deserializeBeanInfo.getFieldList();
            Object v;
            FieldInfo getterfield;
            FieldInfo setterfidld;

            for (int j = 0; j < getters.size(); j++) {

                getterfield=getters.get(j);
                for (int i = 0; i < setters.size(); i++) {
                    setterfidld=setters.get(i);
//                    System.out.println(setterfidld.getName());
//                    System.out.println(getterfield.getName());

                    if (setterfidld.getName().compareTo(getterfield.getName()) == 0) {
                        v = getterfield.getMethod().invoke(bo);
                       setterfidld.getMethod().invoke(so,v);
                        break;
                    }

                }
            }
        } catch (Exception ex) {
            System.out.println(ex.toString());
        }


    }


}

public class SubClass extends  BaseClass {

    private Date birthday;


    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }
}


public class BaseClass {

    private  Integer i;
    private Boolean b;

    private  Boolean is;
    private  Boolean isa;

    private  String whatname;


    public Boolean getB() {
        return b;
    }

    public void setB(Boolean b) {
        this.b = b;
    }

    public Integer getI() {
        return i;
    }

    public void setI(Integer i) {
        this.i = i;
    }

    public Boolean getIs() {
        return is;
    }

    public void setIs(Boolean is) {
        this.is = is;
    }

    public Boolean getIsa() {
        return isa;
    }

    public void setIsa(Boolean isa) {
        this.isa = isa;
    }

    public String getWhatname() {
        return whatname;
    }

    public void setWhatname(String whatname) {
        this.whatname = whatname;
    }
}

测试了一下性能：

   @Test
    public void Test() throws InvocationTargetException, IllegalAccessException {


        BaseClass baseClass = new BaseClass();
        SubClass subClass=new SubClass();

        baseClass.setB(true);
        baseClass.setI(1010);
        baseClass.setIs(false);
        baseClass.setWhatname("fgq");


        Integer i=0;
        List<Integer> ii=new ArrayList<Integer>();
        ii.add(1);
        ii.add(10);
        ii.add(100);
        ii.add(1000);
        ii.add(10000);

        StopWatch stopWatch=new StopWatch();

        stopWatch.reset();;
        stopWatch.start();
        Copyer.Copy(baseClass, subClass);
        stopWatch.stop();
        System.out.println("cache the reflection:"+String.valueOf(stopWatch.getTime()));




        for (int j = 0; j < ii.size(); j++) {
            i=0;
            stopWatch.reset();;
            stopWatch.start();
            while ( i<ii.get(j)) {

                Copyer.Copy(baseClass, subClass);
                subClass.setBirthday(new Date());
                i+=1;
            }
            stopWatch.stop();
            System.out.println(String.format("%s  %s",ii.get(j),String.valueOf(stopWatch.getTime())));
        }




        System.out.println(JSON.toJSONString(subClass,SerializerFeature.PrettyFormat,SerializerFeature.UseISO8601DateFormat));


    }

性能结果为：

cache the reflection:120
1 1
10 7
100 53
1000 139
10000 634

感觉还行。呵呵