我在 Spring 的 BeanUtils 踩到的那些坑，千万不要犯！
程序员大白
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2021-03-23 23:30
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private List<Order> orders;
private AddRequest.Ticket ticket;
private List<Payment> payments;
@ToString
@Data
public class CopyTest1 {
public String outerName;
public CopyTest1.InnerClass innerClass;
public List<CopyTest1.InnerClass> clazz;
@ToString
@Data
public static class InnerClass {
public String InnerName;
}
}
@ToString
@Data
public class CopyTest2 {
public String outerName;
public CopyTest2.InnerClass innerClass;
public List<CopyTest2.InnerClass> clazz;
@ToString
@Data
public static class InnerClass {
public String InnerName;
}
}
CopyTest1 test1 = new CopyTest1();
test1.outerName = "hahaha";
CopyTest1.InnerClass innerClass = new CopyTest1.InnerClass();
innerClass.InnerName = "hohoho";
test1.innerClass = innerClass;
System.out.println(test1.toString());
CopyTest2 test2 = new CopyTest2();
BeanUtils.copyProperties(test1, test2);
System.out.println(test2.toString());
CopyTest1 test1 = new CopyTest1();
test1.outerName = "hahaha";
CopyTest1.InnerClass innerClass = new CopyTest1.InnerClass();
innerClass.InnerName = "hohoho";
test1.innerClass = innerClass;
System.out.println(test1.toString());
CopyTest2 test2 = new CopyTest2();
test2.innerClass = new CopyTest2.InnerClass();
BeanUtils.copyProperties(test1, test2);
BeanUtils.copyProperties(test1.innerClass, test2.innerClass);
System.out.println(test2.toString());
总结
Spring的BeanUtils的CopyProperties方法需要对应的属性有getter和setter方法； 如果存在属性完全相同的内部类，但是不是同一个内部类，即分别属于各自的内部类，则spring会认为属性不同，不会copy； 泛型只在编译期起作用，不能依靠泛型来做运行期的限制； 最后，spring和apache的copy属性的方法源和目的参数的位置正好相反，所以导包和调用的时候都要注意一下。
最后的最后
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;
}
PropertyDescriptor[] targetPds = getPropertyDescriptors(actualEditable);
List<String> ignoreList = ignoreProperties != null ? Arrays.asList(ignoreProperties) : null;
PropertyDescriptor[] var7 = targetPds;
int var8 = targetPds.length;
for(int var9 = 0; var9 < var8; ++var9) {
PropertyDescriptor targetPd = var7[var9];
Method writeMethod = targetPd.getWriteMethod();
if (writeMethod != null && (ignoreList == null || !ignoreList.contains(targetPd.getName()))) {
PropertyDescriptor sourcePd = getPropertyDescriptor(source.getClass(), targetPd.getName());
if (sourcePd != null) {
Method readMethod = sourcePd.getReadMethod();
if (readMethod != null && ClassUtils.isAssignable(writeMethod.getParameterTypes()[0], readMethod.getReturnType())) {
try {
if (!Modifier.isPublic(readMethod.getDeclaringClass().getModifiers())) {
readMethod.setAccessible(true);
}
Object value = readMethod.invoke(source);
if (!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers())) {
writeMethod.setAccessible(true);
}
writeMethod.invoke(target, value);
} catch (Throwable var15) {
throw new FatalBeanException("Could not copy property '" + targetPd.getName() + "' from source to target", var15);
}
}
}
}
}
}
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