SpringBoot连接MySQL
2022年7月2日
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。
