Spring Boot教程（四）Spring Boot 连接MySql数据库

来源素文宅博客：https://blog.yoodb.com/yoodb/article/detail/1416

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。

1. 集成Mybatis
   添加mybatis依赖，在pom.xml文件中增加如下：
   
   org.mybatis.spring.boot
   mybatis-spring-boot-starter
   1.0.0
   

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 {

@Autowiredprivate 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 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);}

}