...
#RequiredArgsContructor(onConstructor_ = {#Lazy})
Class A{
private final B b;
#Lazy
private final C c;
}
Class A{
private final B b;
private final C c;
A(B b,#Lazy C c){
this.b = b;
this.c = c;
}
}
Is it Same?
I want to using #Lazy with #RequiredArgsConstructor
I want to using #Lazy with #RequiredArgsConstructor
It's not the same. When you put #Lazy over constructor it leads to the creation of a lazy-resolution proxy for all affected dependencies, i.e. in your first case both b and c injected into constructor are resolved lazily.
In the second case only c is resolved lazily.
See Is using `#Lazy` on a component constructor equal to annotating every argument?
I want to using #Lazy with #RequiredArgsConstructor
Use your first approach.
P.S. Btw, having #Lazy over constructor in the first case makes redundant #Lazy over private final C c;.
Related
I have been coding basic java for a while and now experiencing to spring boot.
It is very often to see annotation in spring boot.
To me, annotation is to save time for developer to implement less code, by definition online. But this doesn't satisfy my question below
So far, I am experiencing #autowired. What confused me is that #autowired enable dependency injection and tell bean to configure xml (which i dont understand how useful it is yet)
For example,
class A {
private int id;
// With setter and getter method
}
class B {
private String name;
#Autowired
A a;
B(A a){this.a = a} ;
}
}
However, isnt it that, in basic java, it has been allowing to pass instance as argument without #autowired? Why does this suddenly become a benefit? or what am I missing?
class A {
private int id;
// With setter and getter method
}
class B {
private String name;
A a;
B(A a){this.a = a} ;
}
}
You get a benefit when you do this (although it is not recommended)
#Component
class A {
private int id;
// With setter and getter method
}
#Component
class B {
private String name;
#Autowired
A a;
B() {
}
}
now, assuming these classes live in the same or a sub-package of the #SpringBootApplication annotated class, will be auto-configured for you, and A will be injected into B using reflection by the Spring framework.
However, as I mentioned this is not recommended and you probably want to inject it through the constructor, since that makes your component easier to test (you can easily inject a mock in stead). Note that when you have a component/bean with a constructor that takes arguments #Autowired is inferred and spring will try to find the beans to inject into it for you.
#Component
class A {
private int id;
// With setter and getter method
}
#Component
class B {
private String name;
final A a;
B(A a) {
this.a = a;
}
}
If there are two beans of the same type but with different names. Will spring Autowire the bean based on the name without us adding #Qualifier on the variable? I saw in the documentation, "As a fallback Spring uses the bean name as a default qualifier value".
#Component
class A{
}
#Component
class B extends A{
}
class C{
#AutoWired
A a;
//Will a be of type class A, even without #Qualifier...?
}
If there are two beans of the same type but with different names. Will spring Autowire the bean based on the name without us adding #Qualifier on the variable?
#Autowire in the first place cares about type, later about the name. You will get exception saying that there are multiple candidates for injection while only 1 is expected.
#Resource on the other hand, cares about name first, type later.
In this case, B will get injected because there is an A and a B for Spring to choose from and only one of them matches what the #Autowired field is asking for (Class B, because A is not assignable to B).
However, if you had two B's, you would have to qualify it or mark one of them as the primary.
For example, given this:
#Configuration
public class MyConfig {
#Bean
public B example1() {
return new B();
}
#Bean
public B example2() {
return new B();
}
}
Well, now you have two instances of B, with different names. You can fix this one of two ways:
Qualify your Autowire
Note that I'm using field injection here, you really should use constructor, I'm doing it to save space.
#Component
public class SomeComponent {
#Autowired
#Qualifier("example1")
private B b;
}
Or
Mark A Bean as Primary
Redefine the beans, marking one as #Primary
#Configuration
public class MyConfig {
#Bean
#Primary // <-------- NEW!
public B example1() {
return new B();
}
#Bean
public B example2() {
return new B();
}
}
And then inject without needing to name it:
#Component
public class SomeComponent {
#Autowired // (Will pick Primary)
private B b;
}
I am looking for solution where I can use Autowired annotation on some beans which get injected while I Inject Mocks for the main bean.
I have some class A like this and I want to use Autowired D instead of mocked D in Test class. I am using spring boot version 2.0 . Please let me know if someone knows any solution for this.
#Repository
Class A{
B b;
C c;
D d;
#Autowired
public A(B b, C c, D d)
{
this.a =a;
this.b = b;
this.c = c;
}
}
And I am trying to achieve this by Using Mockito as well some Autowired annotation for some dependency. I don't want to Mock D . This approach isn't working I want to know what I can do to make this working. If anyone has used Mockito along with Autowired annotation.
#RunWith(SpringJUnit4ClassRunner.class)
Class ATest{
#Autowired
#InjectMocks
A a;
#Mock
B b;
#Mock
C c;
#Autowired
D d;
}
Since you are trying do write unit test, you can use mockito to run which you are already using.
#RunWith(MockitoJUnitRunner.class)
Class ATest{
#InjectMocks
A a = new A();
#Mock
B b;
#Mock
C c;
#Mock
D d;
}
I got solution to my problem, If I user #Spy annotation instead of #Mock on object to Type D in test class it will invoke actual instead of Mock.
I have 3 classes say for example: A, B and C. all these three classes are independent to each other. there is no parent child relationship. In class c, if I want to use A and B without using getBean method how to inject and use it in class c?
Is there any other way to do it in spring latest version. Please provide your inputs.
you can use autowiring to inject A and B in C:
#Component
public class A {
...
}
#Component
public class B {
...
}
#Component
public class C {
#Autowired
private A a;
#Autowired
private B b;
... use A and B ..
}
My code:
#Component
public class A {
#Autowired
private B b;
public void method() {}
}
public interface X {...}
#Component
public class B implements X {
...
}
I want to test in isolation class A. Do I have to mock class B? If yes, how? Because it is autowired and there is no setter where i could send the mocked object.
I want to test in isolation class A.
You should absolutely mock B, rather than instantiate and inject an instance of B. The point is to test A whether or not B works, so you should not allow a potentially broken B interfere with the testing of A.
That said, I highly recommend Mockito. As mocking frameworks go, it is extremely easy to use. You would write something like the following:
#Test
public void testA() {
A a = new A();
B b = Mockito.mock(B.class); // create a mock of B
Mockito.when(b.getMeaningOfLife()).thenReturn(42); // define mocked behavior of b
ReflectionTestUtils.setField(a, "b", b); // inject b into the B attribute of A
a.method();
// call whatever asserts you need here
}
Here's an example of how I got my tests working with Spring 3.1, JUnit 4.7, and Mockito 1.9:
FooService.java
public class FooService {
#Autowired private FooDAO fooDAO;
public Foo find(Long id) {
return fooDAO.findById(id);
}
}
FooDAO.java
public class FooDAO {
public Foo findById(Long id) {
/* implementation */
}
}
FooServiceTest.java
#RunWith(MockitoJUnitRunner.class)
public class FooServiceTest {
#Mock private FooDAO mockFooDAO;
#InjectMocks private FooService fooService = new FooService();
#Test public final void findAll() {
Foo foo = new Foo(1L);
when(mockFooDAO.findById(foo.getId()).thenReturn(foo);
Foo found = fooService.findById(foo.getId());
assertEquals(foo, found);
}
}
You can inject the field via reflection using Spring's ReflectionTestUtils.setField (or the junit extension PrivateAccessor) or you can create a mock application context and load that. Though for a simple unit (non-integration) test, I favor using reflection for simplicity.
This forum discussion makes sense to me. You can declare your private member b as a type of InterfaceB which is implemented by the class B (ie: service-oriented) then declare a MockB class would also implement the same interface. In your test environment application context, you declare MockB class and your production application context you declare the normal B class and in either case, the code for class A does not need to be changed since it will be auto-wired.