1、Springboot应用获取ApplicationContext

在部分Springboot应用中，经常需要定时任务中执行Spring容器中的Bean。由于定时任务启动不是SpringMVC Controler层触发，因此不能采用@Autoward自动注入容器中的Bean。这时，我们可用编写一个BeanUtils类，可以在任意环境获取Spring容器中的Bean。

1.1、定义Springboot应用启动后执行类

package com.example.demo.common.config;

import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.stereotype.Component;

@Component //添加注解，以便Spring启动时扫描本类，并且需要实现ApplicationContextInitializer接口
public class CustomApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {

    private static ConfigurableApplicationContext context = null;//定义静态类型变量
    /**
     * spring启动后执行本函数，获取context并给static类型变量赋值
      */
    @Override 
    public void initialize(ConfigurableApplicationContext applicationContext) {
        context = applicationContext;
    }
    
    /**
     * 根据class获取是容器中的实现类，class参数可以时接口的class
     * @param <T>
     * @param clzz
     * @return 容器中的实现类实例
     */
    public static <T> T getBean(Class<T> clzz) {
        return context.getBean(clzz);
    }
}

1.2、修改Springboot启动类

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import com.example.demo.common.config.CustomApplicationContextInitializer;

@SpringBootApplication
public class DemoApplication {
    public static void main(String[] args) {
        //SpringApplication.run(DemoApplication.class, args);
        SpringApplication application = new SpringApplication(DemoApplication.class);
        application.addInitializers(new CustomApplicationContextInitializer()); //添加容器启动初始化类
        application.run(args);
    }
}

即可在任意类中即可通过CustomApplicationContextInitializer.getBean(IHelloService.class)方法获取容器中的IHelloService接口的实现类实例。还可以添加根据id获取容器中的实现类的方法。

2、Springboot整合mybatis

2.1、添加durid及mybatis依赖

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid-spring-boot-starter</artifactId>
    <version>1.2.11</version>
</dependency>
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.2.2</version>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.29</version>
</dependency>

2.2、配置数据源及mybatis mapper等相关信息

spring:
  datasource:
    druid:
      url: jdbc:mysql://localhost:3306/testdb?useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghai&zeroDateTimeBehavior=convertToNull
      #url: jdbc:mysql://localhost:3306/testdb?serverTimezone=Asia/Shanghai
      username: testuser
      password: password
      driver-class-name: com.mysql.cj.jdbc.Driver

mybatis:
  mapper-locations:
  - classpath:mappers/**/*.xml #mapper文件存储目录，**表示任意多级目录

2.3、编写数据库访问层接口及mapper文件

package com.example.demo.hello.dao;

import java.util.List;

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

import com.example.demo.hello.vos.FirstTable;

@Mapper //自动在Spring容器中生成本接口实现类，并可以通过@Autoward注入到Service层代码中
@Repository
public interface IHelloDao {
    public List<FirstTable> queryData();
    public int insertData();
}

mapper文件，注意namespace的值和接口类全限定名一致

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.demo.hello.dao.IHelloDao">
    <resultMap id="queryMap" type="com.example.demo.hello.vos.FirstTable">
        <id column="id_col" jdbcType="VARCHAR" property="idCol"/>
        <result column="name_col" jdbcType="VARCHAR" property="nameCol"/>
        <result column="age_col" jdbcType="INTEGER" property="ageCol"/>
    </resultMap>
    
    <select id="queryData" resultMap="queryMap">
        SELECT id_col, name_col, age_col
        FROM first_table
    </select>
    <insert id="insertData">
        INSERT INTO first_table (id_col, name_col, age_col)
        VALUES('0000000000000002', '新增数据', 20);
    </insert>
</mapper>

之后即可在Service实现类中注入接口（不必编写IHelloDao的接口实现类），调用相关方法完成数据库访问操作。