首页 > 代码库 > Java:通过反射复制父类字段到子类。
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。
1 import java.beans.Statement; 2 import java.lang.reflect.Field; 3 import java.lang.reflect.Method; 4 import java.lang.reflect.Type; 5 import java.util.List; 6 7 import com.alibaba.fastjson.JSON; 8 import com.alibaba.fastjson.util.DeserializeBeanInfo; 9 import com.alibaba.fastjson.util.FieldInfo;10 import com.alibaba.fastjson.util.TypeUtils;11 12 /**13 * Created by fenggqc on 2016/6/29.14 */15 public class Copyer {16 17 18 public static <B, S extends B> void Copy(B bo, S so) throws IllegalAccessException {19 20 try {21 Class bc = bo.getClass();22 if (bo == null || so == null) {23 return;24 }25 26 27 DeserializeBeanInfo deserializeBeanInfo = DeserializeBeanInfo.computeSetters(so.getClass(), (Type) so.getClass());28 List<FieldInfo> getters = TypeUtils.computeGetters(bo.getClass(), null);29 30 List<FieldInfo> setters = deserializeBeanInfo.getFieldList();31 Object v;32 FieldInfo getterfield;33 FieldInfo setterfidld;34 35 for (int j = 0; j < getters.size(); j++) {36 37 getterfield=getters.get(j);38 for (int i = 0; i < setters.size(); i++) {39 setterfidld=setters.get(i);40 // System.out.println(setterfidld.getName());41 // System.out.println(getterfield.getName());42 43 if (setterfidld.getName().compareTo(getterfield.getName()) == 0) {44 v = getterfield.getMethod().invoke(bo);45 setterfidld.getMethod().invoke(so,v);46 break;47 }48 49 }50 }51 } catch (Exception ex) {52 System.out.println(ex.toString());53 }54 55 56 }57 58 59 }
1 public class SubClass extends BaseClass { 2 3 private Date birthday; 4 5 6 public Date getBirthday() { 7 return birthday; 8 } 9 10 public void setBirthday(Date birthday) {11 this.birthday = birthday;12 }13 }14 15 16 public class BaseClass {17 18 private Integer i;19 private Boolean b;20 21 private Boolean is;22 private Boolean isa;23 24 private String whatname;25 26 27 public Boolean getB() {28 return b;29 }30 31 public void setB(Boolean b) {32 this.b = b;33 }34 35 public Integer getI() {36 return i;37 }38 39 public void setI(Integer i) {40 this.i = i;41 }42 43 public Boolean getIs() {44 return is;45 }46 47 public void setIs(Boolean is) {48 this.is = is;49 }50 51 public Boolean getIsa() {52 return isa;53 }54 55 public void setIsa(Boolean isa) {56 this.isa = isa;57 }58 59 public String getWhatname() {60 return whatname;61 }62 63 public void setWhatname(String whatname) {64 this.whatname = whatname;65 }66 }
测试了一下性能：
1 @Test 2 public void Test() throws InvocationTargetException, IllegalAccessException { 3 4 5 BaseClass baseClass = new BaseClass(); 6 SubClass subClass=new SubClass(); 7 8 baseClass.setB(true); 9 baseClass.setI(1010);10 baseClass.setIs(false);11 baseClass.setWhatname("fgq");12 13 14 Integer i=0;15 List<Integer> ii=new ArrayList<Integer>();16 ii.add(1);17 ii.add(10);18 ii.add(100);19 ii.add(1000);20 ii.add(10000);21 22 StopWatch stopWatch=new StopWatch();23 24 stopWatch.reset();;25 stopWatch.start();26 Copyer.Copy(baseClass, subClass);27 stopWatch.stop();28 System.out.println("cache the reflection:"+String.valueOf(stopWatch.getTime()));29 30 31 32 33 for (int j = 0; j < ii.size(); j++) {34 i=0;35 stopWatch.reset();;36 stopWatch.start();37 while ( i<ii.get(j)) {38 39 Copyer.Copy(baseClass, subClass);40 subClass.setBirthday(new Date());41 i+=1;42 }43 stopWatch.stop();44 System.out.println(String.format("%s %s",ii.get(j),String.valueOf(stopWatch.getTime())));45 }46 47 48 49 50 System.out.println(JSON.toJSONString(subClass,SerializerFeature.PrettyFormat,SerializerFeature.UseISO8601DateFormat));51 52 53 }
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
Java:通过反射复制父类字段到子类。
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