org.sonar.l10n.java.rules.java.S6818.html Maven / Gradle / Ivy

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Why is this an issue?
@Autowired is an annotation in the Spring Framework for automatic dependency injection. It tells Spring to automatically provide the
required dependencies (such as other beans or components) to a class’s fields, methods, or constructors, allowing for easier and more flexible
management of dependencies in a Spring application. In other words, it’s a way to wire up and inject dependencies into Spring components
automatically, reducing the need for manual configuration and enhancing modularity and maintainability.
In any bean class, only one constructor is permitted to declare @Autowired with the required attribute set to true. This
signifies the constructor to be automatically wired when used as a Spring bean. Consequently, when the required attribute remains at its default value
(true), only a singular constructor can bear the @Autowired annotation. In cases where multiple constructors have this annotation, they
must all specify required=false to be eligible as candidates for auto-wiring.
How to fix it
To maintain code clarity and ensure that the Spring context can create beans correctly, have only one constructor annotated with
@Autowired within a Spring component or set required = false.
Code examples
Noncompliant code example
@Component
public class MyComponent {
  private final MyService myService;

  @Autowired
  public MyComponent(MyService myService) {
    this.myService = myService;
    // ...
  }

  @Autowired  // Noncompliant
  public MyComponent(MyService myService, Integer i) {
    this.myService = myService;
    // ...
  }

  @Autowired  // Noncompliant
  public MyComponent(MyService myService, Integer i, String s) {
    this.myService = myService;
    // ...
  }
}

Compliant solution
@Component
public class MyComponent {
  private final MyService myService;

  @Autowired
  public MyComponent(MyService myService) {
    this.myService = myService;
    // ...
  }

  public MyComponent(MyService myService, Integer i) {
    this.myService = myService;
    // ...
  }

  public MyComponent(MyService myService, Integer i, String s) {
    this.myService = myService;
    // ...
  }
}

Noncompliant code example
@Component
public class MyComponent {
  private final MyService myService;

  @Autowired
  public MyComponent(MyService myService) {
    this.myService = myService;
    // ...
  }

  @Autowired  // Noncompliant
  public MyComponent(MyService myService, Integer i) {
    this.myService = myService;
    // ...
  }

  @Autowired  // Noncompliant
  public MyComponent(MyService myService, Integer i, String s) {
    this.myService = myService;
    // ...
  }
}

Compliant solution
@Component
public class MyComponent {
  private final MyService myService;

  @Autowired
  public MyComponent(MyService myService) {
    this.myService = myService;
    // ...
  }

  @Autowired(required=false)  // Compliant
  public MyComponent(MyService myService, Integer i) {
    this.myService = myService;
    // ...
  }

  @Autowired(required=false)  // Compliant
  public MyComponent(MyService myService, Integer i, String s) {
    this.myService = myService;
    // ...
  }
}

Resources
Documentation

   Spring Framework - Using @Autowired
  

Articles & blog posts

   Baeldung - Guide to Spring @Autowired