I have a project structure similar to the one linked here: https://stackoverflow.com/a/29583882/1243462 . I have a util library containing a Service class in one JAR, meant to be consumed from another Java library/Maven project. However, my Service class itself uses Constructor Injection. So, where the original question had:
#Service
public class PermissionsService { ... }
I have
#Service
public class PermissionsService {
public PermissionsService(#Autowired PermissionsDao dao) {
//assign private dao field to autowired dao
}
}
And, like the original post, I want to create an instance of PermissionsService and inject it into my client/consumer application. I'm not sure of how to create a Configuration class.
#Configuration
public class PersistenceConfig {
public PermissionsService getPermissionsServiceBean() {
//What goes here?
}
}
For now, I have a workaround where I replaced the #Autowired PermissionsDao constructor argument with a field injection, and having a no-args constructor. This allows me to:
#Configuration
public class PersistenceConfig {
public PermissionsService getPermissionsServiceBean() {
return new PermissionsService();
}
}
But, since Field injection is discouraged, what is the right way to structure this code?
In your main module
#Configuration
#Import(PersistenceConfig.class)
public class ServiceConfig() {
}
In your utils module
#Configuration
#ComponentScan(basePackages = {"path-to-persistence-service-and-any-dependencies"})
public class PersistenceConfig {
}
The fact that you use constructor injection for PermissionsDao should not matter if you get the configuration right.
Related
Colleagues, hello! Is is possible to inject beans inside of class which is created via 'new' operator?
For example:
public class TestClass implements Callback {
#Inject
TestClassRepository repository;
//just only methods...
}
And 'TestClass' is created from another class:
Flyway.configure().collbacks(new TestClass()).load();
I have an issue with this,because 'repository.anyMethods()' inside of TestClass creates 'NullPointer' exception.
'TestClassRepository' is marked with the '#ApplicationScoped' and '#Startup' annotations.
#Singleton
public class TestConfig {
#javax.enterprise.inject.Produces
public TestClass testClass() {
return new TestClass();
}
}
another class annotated with the #ApplicationsScoped or #Singleton:
#Inject
public void method(TestClass testClass) {
Flyway.configure().collbacks(testClass).load();
// your code
}
If you create an object by yourself calling a constructor (new TestClass()) then quarkus doesn't manipulate that object, and doesn't inject a repository.
No you cannot inject beans inside a class that is instanciate with the new keyword.
But you can still find a way around like so :
#Dependent
public class BeanFactory {
#Inject
TestClassRepository repository
#Produces
public TestClass createTestClass() {
return new TestClass(this.repository);
}
You can find more details here : Quarkus Contexts and dependency Injection
Also you can define multiple beans for different profiles as mentionned few lines bellow Here
This means you can create a repository for your tests and one for prod or whatever is best for your case.
Also I do not think the annotation "#Startup" would add anything to your TestClassRepository bean.
I am creating a REST service in Spring boot. I am creating a bean in config class and trying to use in service class by auto wiring, but I am always getting null, I have tried in constructor injection as well but not working. Below is the code,
Main app
#SpringBootApplication
public class Main {
public static void main(String[] args) {
SpringApplication.run(Main.class, args);
}
}
REST controller
#RestController
#RequestMapping("/v1")
public class RestController {
#Autowired
private Service service;
Service
#Service
public class ServiceImpl implements Service {
//This is the bean
#Autowired
private Record record;
public ServiceImpl() { //-----------------> tried injecting in constructor as well
System.out.println(record); //-------------------> null
}
Config class
#Configuration
public class AppConfig {
#Bean
public Record record() {
return new Record("test");
}
}
I noted whenever I remove the record() from config class I get below error
required a bean of type 'com.ns.service.Record' that could not be found
And after adding the method the error is not reported but null is returned, which indirectly means record() is considered as returning the required bean.
I can't find what I am doing wrong please advise.
Project folder structure
I think you're doing everything right conceptually
Spring creates an object first and only after that injects the values (technically done in bean post processors):
So try this:
#Service
public class ServiceImpl implements Service {
//This is the bean
#Autowired
private Record record;
public ServiceImpl() {
// here the record is null - not injected yet
System.out.println(record);
}
#PostConstruct
public void checkThisOut() {
// here print the record
}
You say you've tried constructor injection as well - it should work because spring has to inject something into the constructor of a bean (ServiceImpl) or fail. Please show the code snippet
One this that might be wrong in some level (although it doesn't sound like this from your description) is that you have to put all the #Configuration/#Service annotated classes in the package that is the same or underneath the package where you've created the main class annotated with #SpringBootApplication annotation. It instructs spring boot where to look for the beans.
So make sure your classes obey this rule...
I'm new to spring boot, and I need to know how to use #autowired in an attribute that needs parameters to be instantiated.
Please bear in mind the following illustrative situation. It would be something like this:
public class MyClassA{
public SpecificClass myMethod(){
//some logic
}
}
public class MyClassB extends MyClassA{
#Autowired
MyComponent myComponent (myMethod()); //here is my doubt, because my component needs a parameter to be built
}
#Component
public class MyComponent{
public MyComponent(SpecificClass foo){
this.foo=foo;
}
That's not really proper design if your intention is to work with dependency injection. There shouldn't be a direct dependency to the superclass' method like that. Injecting the dependencies indirectly as you're supposed to do would result in something like the following
public class MyClassB extends MyClassA {
#Autowired
private MyComponent myComponent;
}
#Configuration
public class SomeConfig {
#Bean
#Autowired
public MyComponent createComponent(SpecificClass foo) {
// SpecificClass is also injected, providing another layer of indirection
return new MyComponent(foo);
}
}
#Autowired only tells Spring to inject a component into a constructor, field, or method parameter. The injected component is instantiated by the bean container before that. I assume what you are looking for is a way to create MyComponent in such a way that it also receives a Spring Bean.
In your example you could achieve this with the following
#Configuration
public class MyClassA{
#Bean //the bean would have the name 'myMethod', so maybe change that
public SpecificClass myMethod(){
//some logic
}
}
//this needs to be a component, service, ...
#Component
public class MyClassB {
#Autowired
MyComponent myComponent;
}
#Component
public class MyComponent{
#Autowired //Spring wires the Bean 'myMethod' in here, autowired is not needed in the latest Spring Versions
public MyComponent(SpecificClass foo){
this.foo=foo;
}
}
This is a basic Spring question, and not specific to Spring Boot. To better understand wiring you can take a look at the Spring 4 Framework Reference Documentation.
I'm relatively new to Spring Boot and dependency injection overall, so please forgive any noob things going on here. I'm building an API and am having trouble when injecting dependencies into a POJO resource (DTO).
When I call the method in the POJO this.numComments = commentSvc.getAllForPhoto(this.getId()); I am getting a NullPointerException. However, when I do this from another spring-managed bean and pass the values into the constructor, it works fine.
After reading around, it looks like I need to do something with aspectJ and Load Time Weaving, but I'm not sure what that would look like in my code.
In essence, my approach looks something like this:
PhotoResource.java (POJO)
public class PhotoResource extends BaseRepresentable {
#Autowired
CommentService commentSvc;
private Long id;
private Integer numComments;
PhotoResource(PhotoEntity entity){
super(entity);
this.setId(entity.getId);
this.numComments = commentSvc.getAllForPhoto(this.getId());
}
}
CommentService.java
#Service
public class CommentService{
public List<CommentResource> getAllForPhoto(Long photoId) {
// code to get all comments for photo
}
}
Application.java
#SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class);
}
}
Spring won't inject the dependency unless you ask the Spring container to manage the bean. In order for commentSvc to be injected into PhotoResource class, you need to annotate it with #Component or #Bean or #Service, e.g.:
#Component
public class PhotoResource extends BaseRepresentable {
#Autowired
CommentService commentSvc;
}
And make sure the package of this class is included into #ComponentScan packages.
Also, the following won't compile:
#Service
public class CommentService(){
You don't need paranthesis to declare a class, it should be:
#Service
public class CommentService{
I have a class that is annotated #Component that was then #Autowired into another class. However, I need to remove this #Component annotation and instead, create it with an #Bean annotated method in the class where its was previously autowired.
Where previously the classes looked like:
#Component
public class MyClass implements IMyClass
{
// Stuff
}
#Configuration
public class MyUsingClass
{
#Autowired
private IMyClass myClass;
private void methodUsingMyClass()
{
myClass.doStuff();
}
}
So now I have removed the #Component annotation and written a #Bean annotated method like this:
public class MyClass implements IMyClass
{
// Stuff
}
#Configuration
public class MyUsingClass
{
#Bean
public IMyClass getMyClass()
{
return new MyClass();
}
....
}
My question is around replacing the previous call of myClass.doStuff() to use the new bean. Do I now pass in a parameter of type MyClass to the private method:
private void methodUsingMyClass(final MyClass myClass)
{
myClass.doStuff();
}
... or do I call this method directly (doesn't seem the correct way to me):
private void methodUsingMyClass()
{
getMyClass().doStuff();
}
... or are neither of these correct?
I think you misunderstand the #Bean annotation. It can be used to create a Bean. So basically spring will scan all classes, will find your #Bean and create a Bean, not more. You can now use this bean, like if you would use one created with <bean></bean>. To actually use the bean you need to either get it from ApplicationContext or #Autowire it. Of course you can still use that function like any other function in your code, to create a new instance of that object, but that would contradict to what you want to achieve with beans
Using Annotations that solutions
public class MyClass implements IMyClass{
private OtherClassInjection otherClassInjection;
private OtherClassInjection2 otherClassInjection2;
MyClass(OtherClassInjection otherClassInjection, OtherClassInjection2 otherClassInjection2){
this.otherClassInjection=otherClassInjection;
this.otherClassInjection2=otherClassInjection2;
}
public void useObject(){
otherClassInjection.user();
}
}
#Bean(name = "myClass")
#Autowired
#Scope("prototype") //Define scope as needed
public MyClass getMyClass(#Qualifier("otherClassInjection") OtherClassInjection otherClassInjection,
OtherClassInjection2 otherClassInjection2) throws Exception
{
return new MyClass(otherClassInjection, otherClassInjection2);
}
that logical, it's work injection #Autowired when create a Bean if context are know that bean, that you will to want inject.
I'm use that way.