idea uses @Autowired annotation to explain the reasons and solutions

When using idea's @Autowired annotation to inject Mapper files, sometimes it will be marked in red, but it does not affect the operation of the project, so what is the reason?

reason

First look at the @Autowired source code:

@Target({ElementType.CONSTRUCTOR, ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD, ElementType.ANNOTATION_TYPE})@Retention(RetentionPolicy.RUNTIME)@Documentedpublic @interface Autowired {/*** Declares whether the annotated dependency is required.* 
Defaults to {@code true}.*/boolean required() default true;

The default value is true, indicating that the @Autowired annotation must inject a non-empty object. The package of the @Autowired annotation comes from:

import org.springframework.beans.factory.annotation.Autowired;

@Mapper's package comes from:

import org.apache.ibatis.annotations.Mapper;

Summary of the reasons for the error: The @Autowired annotation requires a non-empty object, and @Autowired is of SpringFramework, but the object it introduces is the @Mapper annotation of Mybatis, and idea cannot recognize the annotation of Mybatis well, so idea cannot confirm whether the currently injected object is a non-NULL object.

Extended: If the default value of the @Autowired annotation is set to false, no error will be reported

Solution

1). Use the @Resource annotation, which is a java annotation;
2). Turn off the error in Autowired in the idea setting:
3). Add a SpringFramework annotation to the mapper layer, such as @Repository annotation:

@[email protected] interface UserMapper {}

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