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