SpringBoot连接MySQL

Spring Boot可以大大简化持久化任务，几乎不需要写SQL语句，在之前章节“Spring Boot 构建框架”中我们新建了一个Spring Boot应用程序，本章在原有的工程中与数据库建立连接。

Spring Boot有两种方法与数据库建立连接，一种是使用JdbcTemplate，另一种集成Mybatis，下面分别为大家介绍一下如何集成和使用这两种方式。

1. 使用JdbcTemplate

    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-jdbc</artifactId>
    </dependency>

在resource文件夹下添加application.properties配置文件并输入数据库参数，内容如下：

    
    spring.datasource.url=jdbc:mysql://127.0.0.1:3306/test
    spring.datasource.username=root
    spring.datasource.password=123456
    spring.datasource.driver-class-name=com.mysql.jdbc.Driver
    spring.datasource.max-idle=10
    spring.datasource.max-wait=1000
    spring.datasource.min-idle=5
    spring.datasource.initial-size=5
    server.port=8012
    server.session.timeout=10
    server.tomcat.uri-encoding=UTF-8

新建Controller类测试数据库连接，实例如下：

    package com.example.demo;
    import java.util.Iterator;
    import java.util.List;
    import java.util.Map;
    import java.util.Map.Entry;
    import java.util.Set;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.jdbc.core.JdbcTemplate;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    @RestController
    @RequestMapping("/mydb")
    public class DBController {
        @Autowired
        private JdbcTemplate jdbcTemplate;
         
        @RequestMapping("/getUsers")
        public List<Map<String, Object>> getDbType(){
            String sql = "select * from appuser";
            List<Map<String, Object>> list =  jdbcTemplate.queryForList(sql);
            for (Map<String, Object> map : list) {
                Set<Entry<String, Object>> entries = map.entrySet( );
                if(entries != null) {
                    Iterator<Entry<String, Object>> iterator = entries.iterator( );
                    while(iterator.hasNext( )) {
                        Entry<String, Object> entry =(Entry<String, Object>) iterator.next( );
                        Object key = entry.getKey( );
                        Object value = entry.getValue();
                        System.out.println(key+":"+value);
                    }
                }
            }
            return list;
        }
         
        @RequestMapping("/user/{id}")
        public Map<String,Object> getUser(@PathVariable String id){
        Map<String,Object> map = null;
        List<Map<String, Object>> list = getDbType();
        for (Map<String, Object> dbmap : list) {
             
            Set<String> set = dbmap.keySet();
             
            for (String key : set) {
                if(key.equals("id")){    
                    if(dbmap.get(key).equals(id)){
                        map = dbmap;
                    }
                }
            }
        }
        if(map==null)
            map = list.get(0);
        return map;
        }
         
    }

运行App输入地址输出数据库数据。

2. 集成Mybatis

添加mybatis依赖，在pom.xml文件中增加如下：

    <dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>1.0.0</version>
    </dependency>

在resource文件夹下添加application.properties配置文件并输入数据库参数，如下：

    spring.datasource.url=jdbc:mysql://127.0.0.1:3306/test
    spring.datasource.username=root
    spring.datasource.password=123456
    spring.datasource.driver-class-name=com.mysql.jdbc.Driver
    spring.datasource.max-idle=10
    spring.datasource.max-wait=1000
    spring.datasource.min-idle=5
    spring.datasource.initial-size=5
    server.port=8012
    server.session.timeout=10
    server.tomcat.uri-encoding=UTF-8

依次添加mapper的接口类和xml文件，类分别如下：

AppMessageMapper.java

     package com.example.demo.mapper;
    import java.util.List;
    import com.example.demo.bean.AppMessage;
    public interface AppMessageMapper {
        int deleteByPrimaryKey(String id);
        int insert(AppMessage record);
        int insertSelective(AppMessage record);
        AppMessage selectByPrimaryKey(String id);
        int updateByPrimaryKeySelective(AppMessage record);
        int updateByPrimaryKey(AppMessage record);
    
        List<AppMessage> selectAll();
        List<AppMessage> getMessById(String id);
    }

AppMessageMapper.xml

    
     <?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.mapper.AppMessageMapper" >
      <resultMap id="BaseResultMap" type="com.example.demo.bean.AppMessage" >
        <id column="id" property="id" jdbcType="VARCHAR" />
        <result column="message" property="message" jdbcType="VARCHAR" />
        <result column="senddate" property="senddate" jdbcType="TIMESTAMP" />
      </resultMap>
    
      <sql id="Base_Column_List" >
        id, message, senddate
      </sql>
      <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.String" >
        select 
        <include refid="Base_Column_List" />
        from appuser_message where id = #{id,jdbcType=VARCHAR}
      </select>
      <delete id="deleteByPrimaryKey" parameterType="java.lang.String" >
        delete from appuser_message where id = #{id,jdbcType=VARCHAR}
      </delete>
      <insert id="insert" parameterType="com.example.demo.bean.AppMessage" >
        insert into appuser_message (id, message, senddate ) values (#{id,jdbcType=VARCHAR}, #{message,jdbcType=VARCHAR}, #{senddate,jdbcType=TIMESTAMP} )
      </insert>
      <insert id="insertSelective" parameterType="com.example.demo.bean.AppMessage" >
        insert into appuser_message
        <trim prefix="(" suffix=")" suffixOverrides="," >
          <if test="id != null" >id,</if>
          <if test="message != null" >message,</if>
          <if test="senddate != null" >senddate,</if>
        </trim>
        <trim prefix="values (" suffix=")" suffixOverrides="," >
          <if test="id != null" >#{id,jdbcType=VARCHAR},</if>
          <if test="message != null" >#{message,jdbcType=VARCHAR},</if>
          <if test="senddate != null" >#{senddate,jdbcType=TIMESTAMP},</if>
        </trim>
      </insert>
      <update id="updateByPrimaryKeySelective" parameterType="com.example.demo.bean.AppMessage" >
        update appuser_message 
        <set >
          <if test="message != null" >message = #{message,jdbcType=VARCHAR},</if>
          <if test="senddate != null" >senddate = #{senddate,jdbcType=TIMESTAMP},</if>
        </set>
            where id = #{id,jdbcType=VARCHAR}
      </update>
      <update id="updateByPrimaryKey" parameterType="com.example.demo.bean.AppMessage" >
        update appuser_message set message = #{message,jdbcType=VARCHAR}, senddate = #{senddate,jdbcType=TIMESTAMP} where id = #{id,jdbcType=VARCHAR}
      </update>
    
      <select id="selectAll" resultMap="BaseResultMap">
        select id, message, senddate from appuser_message order by senddate asc
      </select>
    
      <select id="getMessById" resultMap="BaseResultMap" parameterType="java.lang.String">
       select id, message, senddate from appuser_message where id = #{id,jdbcType=VARCHAR} order by senddate asc  
      </select>
    </mapper>

AppMessage.java

     package com.example.demo.bean;
    import java.util.Date;
    public class AppMessage {
    private String id;
    private String message;
    private Date senddate;
    public String getId() {
            return id;
        }
        public void setId(String id) {
            this.id = id == null ? null : id.trim();
        }
        public String getMessage() {
            return message;
        }
        public void setMessage(String message) {
            this.message = message == null ? null : message.trim();
        }
        public Date getSenddate() {
            return senddate;
        }
        public void setSenddate(Date senddate) {
            this.senddate = senddate;
        }
    }

AppMessageService.java

    
     package com.example.demo.service;
    import java.util.ArrayList;
    import java.util.List;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    import com.example.demo.bean.AppMessage;
    import com.example.demo.mapper.AppMessageMapper;
    @Service
    public class AppMessageService {
    
        @Autowired
        private AppMessageMapper mapper;
         
        public List<AppMessage> getMessage(){
            List<AppMessage> list = new ArrayList<AppMessage>();
            list.add(mapper.selectByPrimaryKey("xtt"));
            //list = mapper.selectAll();
            return list;
        }
    
        public List<AppMessage> getAllMessage(){
            List<AppMessage> list = new ArrayList<AppMessage>();
            list = mapper.selectAll();
            return list;
        }
        public int addMessage(AppMessage appMessage) {
            return mapper.insert(appMessage);
        }
        public List<AppMessage> getMessageById(String id) {
            return mapper.getMessById(id);
        }
        public int delMessage(String id) {
            return mapper.deleteByPrimaryKey(id);
        }
    }

APPMessageController.java

     package com.example.demo.controller;
    
    import java.util.List;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.RequestBody;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RequestParam;
    import org.springframework.web.bind.annotation.RestController;
    import com.example.demo.bean.AppMessage;
    import com.example.demo.service.AppMessageService;
    
    @RestController
    @RequestMapping("/appmessage")
    public class APPMessageController {
        @Autowired
        private AppMessageService service;
    
        @RequestMapping("/getThree")
        public List<AppMessage> getThreeForMessage() {
    
            List<AppMessage> list = service.getMessage();
            return list;
        }
    
        @RequestMapping("/getAll")
        public List<AppMessage> getAllMessage() {
    
            List<AppMessage> list = service.getAllMessage();
            int num = list.size();
            if (null != list && num > 3) {
                for (int i = 0; i < num - 3; i++) {
                    list.remove(0);
                }
            }
            return list;
        }
    
        @RequestMapping("/getByID")
        public List<AppMessage> getMessageById(@RequestParam("id") String id) {
            List<AppMessage> list = service.getMessageById(id);
            int num = list.size();
            if (null != list && num > 5) {
                for (int i = 0; i < num - 5; i++) {
                    list.remove(0);
                }
            }
            return list;
        }
    
        @RequestMapping(value = "/add", method = RequestMethod.POST) // 或者采用@PostMapping("/add")方法，更加节省代码的编写量
        public int addMessage(@RequestBody AppMessage appMessage) {
            return service.addMessage(appMessage);
        }
    
        @RequestMapping(value = "/delMessageById", method = RequestMethod.POST)
        // 或者采用@PostMapping("/delMessageById")方法，更加节省代码的编写量
        public int delMessageById(@RequestParam("id") String id) {
            return service.delMessage(id);
        }
    }

问题描述？

SpringBoot扫描包提示找不到mapper的问题，异常信息：

Consider defining a bean of type in your configuration

分析原因

Spring Boot项目的Bean装配默认规则是根据Application类所在的包位置从上往下扫描，“Application类”是指Spring Boot项目入口类。如果Application类所在的包为：com.yoodb.blog，则只会扫描com.yoodb.blog包及其所有子包，如果service或dao所在包不在com.yoodb.blog及其子包下，则不会被扫描。

解决方法

方式一：使用注解@ComponentScan(value=”com.yoodb.blog”)，其中，com.yoodb.blog为包路径。

方式二：将启动类Application放在上一级包中，注意的是Application启动类必须要保证在包的根目录下。