大牛公司内部总结：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>`alert("Hello CSDN");`

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。

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.

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。