Spring Boot高级教程之Spring Boot连接MySql数据库

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。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。