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静态工具类中使用@Autowired的方法

静态工具类中使用@Autowired的方法

在Spring项目中我习惯使用@Autowired来注入Service层或者Dao层,在一次偶然我在静态方法中查询数据库数据,而报了NullPointerException,一路找来发现Mapper为Null,分析原因发现Spring不支持依赖注入static静态变量,静态变量/类变量不是对象的属性而是一个类的属性,spring则是基于对象层面上的依赖注入,好了不罗嗦了,下面给出解决方案直接上代码。

静态工具类:

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;

/**

  • @Author: Wenx

  • @Description: 静态工具类中使用@Autowired的方法

  • @Date: Created in 2020/1/13 20:29

  • @Modified By: */ @Component public class DaoUtils { private static final Logger logger = LoggerFactory.getLogger(DaoUtils.class); private static DaoUtils utils;

    @Autowired private TestMapper testMapper;

    @PostConstruct public void init() { utils = this; }

    public static TestDO getTest(Integer id) { TestDO testDO = utils.testMapper.selectTestById(1); return testDO; }

}

Mapper:

import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.springframework.stereotype.Repository;

/**

  • @Author: Wenx

  • @Description:

  • @Date: Created in 2020/1/13 20:32

  • @Modified By: */ @Mapper @Repository public interface TestMapper {

    /**

    • 查询table_test表记录
    • @param id ID
    • @return TestDO */ @Select("select id,name from table_test where id = #{id}") TestDO selectTestById(@Param("id") Integer id);

}

实体:

/**
 * @Author: Wenx
 * @Description:
 * @Date: Created in 2020/1/13 20:35
 * @Modified By:
 */
public class TestDO {
private Integer id;
private String name;


public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

}

启动类:

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;

/**

  • @Author: Wenx

  • @Description: 启动类

  • @Date: Created in 2020/1/13 20:13

  • @Modified By: */ @SpringBootApplication public class StudyDemoApplication { private static final Logger logger = LoggerFactory.getLogger(StudyDemoApplication.class);

    public static void main(String[] args) { ApplicationContext context = SpringApplication.run(StudyDemoApplication.class, args);

     TestDO testDO = DaoUtils.getTest(1);
    

    } }

本文由【Wenx408】发布于开源中国,原文链接:https://my.oschina.net/wenx408/blog/3157922

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