Spring Boot系列（六）Spring Boot 连接MySql数据库

内容简介：Spring Boot系列（六）Spring Boot 连接MySql数据库

这一篇介绍Spring Boot 连接 MySql 数据库，需要springboot实战完整视频教程的，点击 这里 ！

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。

来源： 素文宅博客

链接： https://blog. yood b.com/yoodb/article/detail/1412

以上所述就是小编给大家介绍的《Spring Boot系列（六）Spring Boot 连接MySql数据库》，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对 码农网 的支持！

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