private static void copyProperties(Object source, Object target, @Nullable Class<?> editable, @Nullable String... ignoreProperties) throws BeansException {
Assert.notNull(source, "Source must not be null");
Assert.notNull(target, "Target must not be null");
Class<?> actualEditable = target.getClass();
if (editable != null) {
if (!editable.isInstance(target)) {
throw new IllegalArgumentException("Target class [" + target.getClass().getName() + "] not assignable to Editable class [" + editable.getName() + "]");
}
actualEditable = editable;
}
//獲取目標對象的各屬性信息
PropertyDescriptor[] targetPds = getPropertyDescriptors(actualEditable);
List<String> ignoreList = ignoreProperties != null ? Arrays.asList(ignoreProperties) : null;
PropertyDescriptor[] var7 = targetPds;
int var8 = targetPds.length;
//遍歷各屬性
for(int var9 = 0; var9 < var8; ++var9) {
PropertyDescriptor targetPd = var7[var9];
//獲取目標對象該屬性的寫方法,即set方法
Method writeMethod = targetPd.getWriteMethod();
//判斷該屬性是否在不被copy的屬性集合中
if (writeMethod != null && (ignoreList == null || !ignoreList.contains(targetPd.getName()))) {
//根據目標對象的屬性名稱,獲取源對象的該屬性信息
PropertyDescriptor sourcePd = getPropertyDescriptor(source.getClass(), targetPd.getName());
if (sourcePd != null) {
//獲取源對象的該屬性的讀方法,即get方法
Method readMethod = sourcePd.getReadMethod();
//判斷目標對象的set方法所需的參數類型和源對象get方法的返回類型是否一致
if (readMethod != null && ClassUtils.isAssignable(writeMethod.getParameterTypes()[0], readMethod.getReturnType())) {
try {
//如果源對象的get方法不包含public修飾符,將該方法修改爲可以通過反射外部訪問
if (!Modifier.isPublic(readMethod.getDeclaringClass().getModifiers())) {
readMethod.setAccessible(true);
}
//通過反射獲取源對象該屬性的值
Object value = readMethod.invoke(source);
//如果目標對象的set方法不包含public修飾符,將該方法修改爲可以通過反射外部訪問
if (!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers())) {
writeMethod.setAccessible(true);
}
//通過反射將值寫入目標對象
writeMethod.invoke(target, value);
} catch (Throwable var15) {
throw new FatalBeanException("Could not copy property '" + targetPd.getName() + "' from source to target", var15);
}
}
}
}
}
}
通過copyProperties方法的源代碼可以看出,實現此功能有三個必須條件:
1.需要複製的屬性名要相同;
2.對於要複製的屬性,源對象必須有get方法,目標對象必須有set方法;
3.目標對象的set方法所需的參數類型和源對象get方法的返回類型保持一致。
下面貼上測試類和測試代碼:
被複制的類
public class CopyTest1 {
private String outStr;
private CopyTest1.Inner inner;
private List<Integer> num;
public static class Inner {
public String inStr;
}
public String getOutStr() {
return outStr;
}
public void setOutStr(String outStr) {
this.outStr = outStr;
}
public Inner getInner() {
return inner;
}
public void setInner(Inner inner) {
this.inner = inner;
}
public List<Integer> getNum() {
return num;
}
public void setNum(List<Integer> num) {
this.num = num;
}
@Override
public String toString() {
return "CopyTest1{" +
"outStr='" + outStr + '\'' +
", inner=" + inner +
", num=" + num +
'}';
}
目標類
public class CopyTest2 {
private String outStr;
private CopyTest2.Inner inner;
private List<String> num;
public static class Inner {
public String inStr;
}
public String getOutStr() {
return outStr;
}
public void setOutStr(String outStr) {
this.outStr = outStr;
}
public Inner getInner() {
return inner;
}
public void setInner(Inner inner) {
this.inner = inner;
}
public List<String> getNum() {
return num;
}
public void setNum(List<String> num) {
this.num = num;
}
@Override
public String toString() {
return "CopyTest2{" +
"outStr='" + outStr + '\'' +
", inner=" + inner +
", num=" + num +
'}';
}
}
測試方法
public static void main(String[] args) {
CopyTest1 test1 = new CopyTest1();
test1.setOutStr("hahahaha");
List<Integer> num = new ArrayList();
num.add(1);
test1.setNum(num);
CopyTest1.Inner inner = new CopyTest1.Inner();
inner.inStr = "hohohoho";
test1.setInner(inner);
System.out.println(test1.toString());
CopyTest2 test2 = new CopyTest2();
BeanUtils.copyProperties(test1, test2);
System.out.println(test2.toString());
}
從debug的效果看出屬於兩個類中的內部類,即使類名和屬性名都相同相同,仍然不會複製,因爲目標對象的set方法所需的參數類型和源對象get方法的返回類型是不一致,違反了條件3。因此,內部類需要單獨使用copyProperties方法,複製一遍屬性。
源對象中的list泛型爲Integer,而目標對象中list的泛型爲String,但是泛型只是編譯期起約束作用,運行期可以看出set的參數類型和get的返回類型都是java.util.List,並無約束,因此也可以實現複製。
本文參考:www.jianshu.com/p/357b55852efc