Spring 注释控制器是否一定需要默认构造函数 [英] Does a Spring annotated controller necessarily need a default constructor

问题描述

我有一个使用注解的弹簧控制器.我给了这个控制器一个带有两个参数的构造函数.我想要两种初始化控制器的方式:构造函数注入和 setter 注入.

I have a spring controller that uses annotations. I gave this controller a constructor that takes two arguments. I want both ways of initializing the controller: constructor injection and setter injection.

@Controller("viewQuestionController")
@RequestMapping("/public/viewQuestions")
public class ViewQuestionController
{
    @Resource(name="questionService")
    private QuestionService questionService;

   /*public ViewQuestionController()
 {
    int i=0;
    i++;
 } 
   */   

public ViewQuestionController(@Qualifier("questionService") QuestionService questionService)
{
    this.questionService = questionService;
}

@Resource(name="questionService")
public void setQuestionService(QuestionService questionService)
{
    this.questionService = questionService;
}
}   

当我取消对默认构造函数的注释时，控制器会正确启动.但是，如果我不这样做，我会得到一个 BeanInstantiationException, No default constructor found;嵌套异常是 java.lang.NoSuchMethodException.那么，我对带注释的构造函数的配置是错误的还是在 spring 中完全注释的控制器总是需要一个默认的构造函数?

When I uncomment the default constructor, the controller is initiated correctly. However, if I don't, I get a BeanInstantiationException, No default constructor found; nested exception is java.lang.NoSuchMethodException. So, is my configuration for the annotated constructor wrong or does a completely annotated controller in spring always need a default constructor?

推荐答案

如果想通过注解配置构造函数注入，需要在构造函数上加上相应的注解.我不确定如何使用 @Resource 完成它，但是 @Autowired 和 @Inject 支持它:

If you want to configure constructor injection via annotations, you need to put the corresponding annotation on the constructor. I'm not sure how it can be done with @Resource, but @Autowired and @Inject support it:

@Autowired
public ViewQuestionController(@Qualifier("questionService") QuestionService questionService) 

或

@Inject
public ViewQuestionController(@Named("questionService") QuestionService questionService) 

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