BeanCopier

cglib是一款比较底层的操做java字节码的框架。 

下面经过拷贝bean对象来测试BeanCopier的特性： 

public class OrderEntity {
    private int id;
    private String name;
    // Getters and setters are omitted
}

 

public class OrderDto {
    private int id;
    private String name;
    // Getters and setters are omitted
}

 

public class PropWithDiffType {
    private Integer id;
    private String name;
    // Getters and setters are omitted
}

 

public class LackOfSetter {
    private int id;
    private String name;

    public LackOfSetter() {
    }

    public LackOfSetter(int id, String name) {
        this.id = id;
        this.name = name;
    }
    // Getters and setters are omitted
    // public void setName(String name) {
    //  this.name = name;
    // }
}

1. 属性名称、类型都相同: 

@Test
public void normalCopyTest() {
    OrderEntity entity = new OrderEntity();
    entity.setId(1);
    entity.setName("orderName");
    final BeanCopier copier = BeanCopier.create(OrderEntity.class, OrderDto.class, false);
    OrderDto dto = new OrderDto();
    copier.copy(entity, dto, null);
    Assert.assertEquals(1, dto.getId());
    Assert.assertEquals("orderName", dto.getName());
}

结论：拷贝OK。 

2. 属性名称相同、类型不一样： 

@Test
public void sameNameDifferentTypeCopyTest() {
    OrderEntity entity = new OrderEntity();
    entity.setId(1);
    entity.setName("orderName");
    final BeanCopier copier = BeanCopier.create(OrderEntity.class, PropWithDiffType.class, false);
    PropWithDiffType dto = new PropWithDiffType();
    copier.copy(entity, dto, null);
    Assert.assertEquals(null, dto.getId()); // OrderEntity的id为int类型，而PropWithDiffType的id为Integer类型，不拷贝
    Assert.assertEquals("orderName", dto.getName());
}

结论：名称相同而类型不一样的属性不会被拷贝。 

注意：即便源类型是原始类型(int, short和char等)，目标类型是其包装类型(Integer, Short和Character等)，或反之：都不会被拷贝。 

3. 源类和目标类有相同的属性(二者的getter都存在),但目标类的setter不存在 

@Test
public void targetLackOfSetterCopyTest() {
    OrderEntity entity = new OrderEntity();
    entity.setId(1);
    entity.setName("orderName");
    final BeanCopier copier = BeanCopier.create(OrderEntity.class, LackOfSetter.class, false);  // 抛NullPointerException
    LackOfSetter dto = new LackOfSetter();
    copier.copy(entity, dto, null);
}

结论：建立BeanCopier的时候抛异常。 

致使异常的缘由是BeanCopier类的第128~133行 

for (int i = 0; i < setters.length; i++) { // 遍历目标类的属性描述集
    PropertyDescriptor setter = setters[i];
    PropertyDescriptor getter = (PropertyDescriptor)names.get(setter.getName()); // 从源类获取和目标类属性名称相同的属性描述
    if (getter != null) {
        MethodInfo read = ReflectUtils.getMethodInfo(getter.getReadMethod()); // 获取源类属性的getter方法
        MethodInfo write = ReflectUtils.getMethodInfo(setter.getWriteMethod()); // 获取目标类属性的setter方法。LackOfSetter类name属性的setter方法没有，因此报错

4. 源类或目标类的setter比getter少 

@Test
public void sourceLackOfSetterCopyTest() {
    LackOfSetter source = new LackOfSetter(1, "throne");
    final BeanCopier copier = BeanCopier.create(LackOfSetter.class, OrderDto.class, false);
    OrderDto dto = new OrderDto();
    copier.copy(source, dto, null);
    Assert.assertEquals(1, dto.getId());
    Assert.assertEquals("throne", dto.getName());
}

结论：拷贝OK。此时的setter多余，但不会报错。 

总结： 

1. BeanCopier只拷贝名称和类型都相同的属性。 

2. 当目标类的setter数目比getter少时，建立BeanCopier会失败而致使拷贝不成功。