BeanCopier

cglib是一款比較底層的操做java字節碼的框架。 

下面經過拷貝bean對象來測試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. 屬性名稱、類型都相同: 

@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());
}

結論：拷貝OK。 

2. 屬性名稱相同、類型不一樣： 

@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爲int類型，而PropWithDiffType的id爲Integer類型，不拷貝
    Assert.assertEquals("orderName", dto.getName());
}

結論：名稱相同而類型不一樣的屬性不會被拷貝。 

注意：即便源類型是原始類型(int, short和char等)，目標類型是其包裝類型(Integer, Short和Character等)，或反之：都不會被拷貝。 

3. 源類和目標類有相同的屬性(二者的getter都存在),但目標類的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);  // 拋NullPointerException
    LackOfSetter dto = new LackOfSetter();
    copier.copy(entity, dto, null);
}

結論：建立BeanCopier的時候拋異常。 

致使異常的緣由是BeanCopier類的第128~133行 

for (int i = 0; i < setters.length; i++) { // 遍歷目標類的屬性描述集
    PropertyDescriptor setter = setters[i];
    PropertyDescriptor getter = (PropertyDescriptor)names.get(setter.getName()); // 從源類獲取和目標類屬性名稱相同的屬性描述
    if (getter != null) {
        MethodInfo read = ReflectUtils.getMethodInfo(getter.getReadMethod()); // 獲取源類屬性的getter方法
        MethodInfo write = ReflectUtils.getMethodInfo(setter.getWriteMethod()); // 獲取目標類屬性的setter方法。LackOfSetter類name屬性的setter方法沒有，因此報錯

4. 源類或目標類的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());
}

結論：拷貝OK。此時的setter多餘，但不會報錯。 

總結： 

1. BeanCopier只拷貝名稱和類型都相同的屬性。 

2. 當目標類的setter數目比getter少時，建立BeanCopier會失敗而致使拷貝不成功。