spring boot整合mybatis使用c3p0数据源连接mysql

刚刚接触springboot，对很多东西都不熟悉，例如，它的注解方式，他的配置方式等；听说它很牛逼，所以就尝试着去学习。在基本熟悉springboot的第一个程序之后。想到当时spring整合mybatis时使用了数据源连接数据库，所以自己也想尝试使用c3p0连接数据库。所以就有了以下的内容：

首先第一步，创建maven项目导入包：

pom.xml

									<parent>

									    <groupId>org.springframework.boot</groupId>

									    <artifactId>spring-boot-starter-parent</artifactId>

									    <version>1.4.1.RELEASE</version>

									  </parent>

									  <dependencies>

									    <dependency>

									      <groupId>junit</groupId>

									      <artifactId>junit</artifactId>

									      <version>4.12</version>

									      <scope>test</scope>

									    </dependency>

									    <dependency>

									      <groupId>org.springframework.boot</groupId>

									      <artifactId>spring-boot-starter-test</artifactId>

									      <version>1.4.1.RELEASE</version>

									    </dependency>

									    <dependency>

									      <groupId>org.springframework.boot</groupId>

									      <artifactId>spring-boot-starter-web</artifactId>

									      <version>1.4.1.RELEASE</version>

									    </dependency>

									    <dependency>

									      <groupId>org.mybatis.spring.boot</groupId>

									      <artifactId>mybatis-spring-boot-starter</artifactId>

									      <version>1.1.1</version>

									    </dependency>

									    <dependency>

									      <groupId>mysql</groupId>

									      <artifactId>mysql-connector-java</artifactId>

									      <version>5.1.33</version>

									    </dependency>

									    <dependency>

									      <groupId>c3p0</groupId>

									      <artifactId>c3p0</artifactId>

									      <version>0.9.1.2</version>

									    </dependency>

									  </dependencies>

									  <build>

									    <plugins>

									      <plugin>

									        <groupId>org.springframework.boot</groupId>

									        <artifactId>spring-boot-maven-plugin</artifactId>

									      </plugin>

									    </plugins>

									  </build>

应用服务类

				?

									import org.mybatis.spring.annotation.MapperScan;

									import org.springframework.boot.SpringApplication;

									import org.springframework.boot.autoconfigure.EnableAutoConfiguration;

									import org.springframework.boot.autoconfigure.SpringBootApplication;

									@SpringBootApplication

									@MapperScan(value="com.myk.spring.t3")//扫描mapper包

									@EnableAutoConfiguration//自动载入应用程序所需的所有Bean，当使用Exclude这个属性时，是禁止自动配置某个类

									public class Application {

									  public static void main(String[] args) {

									    SpringApplication.run(Application.class, args);

									  }

									}

配置文件内容（配置数据库）

				?

									datasource: 

									 url: jdbc:mysql://ip:port/databaseName

									 driver-class: com.mysql.jdbc.Driver

									 username: ***

									 password: ***

准备无误，尝试启用应用服务，没有报错即可继续配置数据源，尝试很多方法，自己注入是不可能的，所以，我就想到spring的配置，尝试按照那样的方式去配置，所以，DataSourceConfig.java

				?

									import javax.sql.DataSource;

									import org.mybatis.spring.SqlSessionFactoryBean;

									import org.springframework.beans.factory.annotation.Qualifier;

									import org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder;

									import org.springframework.boot.context.properties.ConfigurationProperties;

									import org.springframework.context.annotation.Bean;

									import org.springframework.context.annotation.Configuration;

									import org.springframework.context.annotation.Primary;

									import com.mchange.v2.c3p0.ComboPooledDataSource;

									@Configuration

									public class DataSourceConfig {

									  @Bean(name="dataSource")

									  @Qualifier(value="dataSource")//限定描述符除了能根据名字进行注入，但能进行更细粒度的控制如何选择候选者

									  @Primary//用@Primary区分主数据源

									  @ConfigurationProperties(prefix="c3p0.primary")//指定配置文件中，前缀为c3p0的属性值

									  public DataSource dataSource(){

									    return DataSourceBuilder.create().type(ComboPooledDataSource.class).build();//创建数据源

									  }

									  /**

									  *返回sqlSessionFactory

									  */

									  @Bean

									  public SqlSessionFactoryBean sqlSessionFactoryBean(){

									    SqlSessionFactoryBean sqlSessionFactory = new SqlSessionFactoryBean();

									    sqlSessionFactory.setDataSource(dataSource());

									    return sqlSessionFactory;

									  }

									}

也许会有疑问，为什么这里只需要一个sqlSessionFactory，这个具体要去熟悉spring整合mybatis。还有看看底层就明白了
这样就可以自动装配了。

数据源都准备好了，尝试连接数据库吧

编辑接口

ExamPleMapper.java

				?

									import java.util.List;

									public interface ExamPleMapper {

									  public List<Users> getUsers();

									}

编辑Mapper xml文件

				?

									<?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.*.ExamPleMapper">

									  <select id="getUsers" resultType="com.*.Users">

									    select * from users

									  </select>

									</mapper>

编辑实体类，因为要将结果反射到bean类中
Users.java

				?

									public class Users {

									  private int userid;

									  private String username;

									  @Override

									  public String toString() {

									    return "Users [userid=" + userid + ", username=" + username + "]";

									  }

									  public int getUserid() {

									    return userid;

									  }

									  public void setUserid(int userid) {

									    this.userid = userid;

									  }

									  public String getUsername() {

									    return username;

									  }

									  public void setUsername(String username) {

									    this.username = username;

									  }

									  public Users(int userid, String username) {

									    super();

									    this.userid = userid;

									    this.username = username;

									  }

									  public Users() {

									    super();

									    // TODO Auto-generated constructor stub

									  }

									}

编辑实现

Example2.java

				?

									import java.util.List;

									import org.springframework.beans.factory.annotation.Autowired;

									import org.springframework.web.bind.annotation.RequestMapping;

									import org.springframework.web.bind.annotation.ResponseBody;

									import org.springframework.web.bind.annotation.RestController;

									@RestController

									@RequestMapping(value="/example2")//映射

									public class Example2 {

									  @Autowired

									  public ExamPleMapper examPleMapper;

									  @ResponseBody

									  @RequestMapping(value="/gu")

									  public List<Users> getUsers(){

									    return examPleMapper.getUsers();

									  }

									}