Spring Boot教程（四）Spring Boot 連接MySql數據庫

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

Spring Boot可以大大簡化持久化任務，幾乎不需要寫SQL語句，在之前章節“Spring Boot 構建框架”中我們新建了一個Spring Boot應用程序，本章在原有的工程中與數據庫建立連接。

Spring Boot有兩種方法與數據庫建立連接，一種是使用JdbcTemplate，另一種集成Mybatis，下面分別爲大家介紹一下如何集成和使用這兩種方式。
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文件夾下添加application.properties配置文件並輸入數據庫參數，內容如下：
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類測試數據庫連接，實例如下：
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;
}

}
運行App輸入地址輸出數據庫數據。

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

在resource文件夾下添加application.properties配置文件並輸入數據庫參數，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的接口類和xml文件，類分別如下：
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 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) // 或者採用@PostMapping("/add")方法，更加節省代碼的編寫量
public int addMessage(@RequestBody AppMessage appMessage){
    return service.addMessage(appMessage);
}

@RequestMapping(value="/delMessageById",method=RequestMethod.POST) // 或者採用@PostMapping("/delMessageById")方法，更加節省代碼的編寫量
public int delMessageById(@RequestParam("id") String id){
        return service.delMessage(id);
}

}