SpringBoot入门系列：第六篇 mybatis

注意一些小细节，主要有三：

1、引入的依赖错误；

2、启动配置错误；

3、xml文件的mapper命名空间错误。

一、完整的pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>springbootTest</groupId> <artifactId>springbootTest</artifactId> <version>0.0.1-SNAPSHOT</version> <!-- Inherit defaults from Spring Boot --> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>1.4.0.BUILD-SNAPSHOT</version> </parent> <!-- Add typical dependencies for a web application --> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-jdbc</artifactId> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <scope>runtime</scope> </dependency> <dependency> <groupId>org.mybatis.spring.boot</groupId> <artifactId>mybatis-spring-boot-starter</artifactId> <version>1.3.0</version> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency> </dependencies> <repositories> <repository> <id>spring-snapshots</id> <url>http://repo.spring.io/snapshot</url> <snapshots> <enabled>true</enabled> </snapshots> </repository> <repository> <id>spring-milestones</id> <url>http://repo.spring.io/milestone</url> </repository> </repositories> <pluginRepositories> <pluginRepository> <id>spring-snapshots</id> <url>http://repo.spring.io/snapshot</url> </pluginRepository> <pluginRepository> <id>spring-milestones</id> <url>http://repo.spring.io/milestone</url> </pluginRepository> </pluginRepositories> <build> <sourceDirectory>src</sourceDirectory> <plugins> <plugin> <artifactId>maven-compiler-plugin</artifactId> <version>3.1</version> <configuration> <source>1.8</source> <target>1.8</target> </configuration> </plugin> </plugins> </build> </project> 比较关键的是：mysql-connector-java、mybatis-spring-boot-starter，其它的根据使用引用。

二、启动文件 Application.java

package com.example; import javax.sql.DataSource; import org.apache.ibatis.session.SqlSessionFactory; import org.mybatis.spring.SqlSessionFactoryBean; import org.mybatis.spring.annotation.MapperScan; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.EnableAutoConfiguration; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.boot.autoconfigure.domain.EntityScan; import org.springframework.boot.context.properties.ConfigurationProperties; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.core.io.support.PathMatchingResourcePatternResolver; import org.springframework.data.jpa.repository.config.EnableJpaRepositories; import org.springframework.jdbc.datasource.DataSourceTransactionManager; import org.springframework.transaction.PlatformTransactionManager; @Configuration //标注一个类是配置类，spring boot在扫到这个注解时自动加载这个类相关的功能，比如前面的文章中介绍的配置AOP和拦截器时加在类上的Configuration @EnableAutoConfiguration() //启用自动配置 该框架就能够进行行为的配置，以引导应用程序的启动与运行, 根据导入的starter-pom 自动加载配置 @EnableJpaRepositories(basePackages={"com.dao"}) //@EnableJpaRepositories(basePackages={"dao层对应的包路径"}) @ComponentScan(value={"com.*","com.dao"})//扫描组件 @ComponentScan(value = "com.spriboot.controller") 配置扫描组件的路径 @SpringBootApplication //@EntityScan("entity对应的包路径") @EntityScan("com.entity") @MapperScan("com.dao") public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } @Bean @ConfigurationProperties(prefix="spring.datasource") public DataSource dataSource() { return new org.apache.tomcat.jdbc.pool.DataSource(); } @Bean public SqlSessionFactory sqlSessionFactoryBean() throws Exception { SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean(); sqlSessionFactoryBean.setDataSource(dataSource()); PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver(); sqlSessionFactoryBean.setMapperLocations(resolver.getResources("classpath:/com/example/mapper/*.xml")); return sqlSessionFactoryBean.getObject(); } @Bean public PlatformTransactionManager transactionManager() { return new DataSourceTransactionManager(dataSource()); } } 注意3点：

1、在类上声明MapperScan，这是mybatis-spring-boot-starter在1.1.1引入的类Mapper，从而在mapper接口上不需要任何声明

2、配置dataSource、SqlSessionFactory、PlatformTransactionManager，其实默认的都已经配好，这里主要是为了标明Mapper的xml文件存在位置

3、src/main/resources下的文件，在打包之后，都在工程的根目录。

这个只需要更改两个地方：

1、MapperScan之后的"com.example.mapper"，改成Mapper接口文件所在的包名

2、sqlSessionFactoryBean方法中"classpath:/mybatis/*.xml"，改成Mapper的xml文件存在位置

三、启动配置文件 application.properties

spring.datasource.url=jdbc:mysql://192.168.1.206:3306/test1?useUnicode=true&characterEncoding=UTF-8 spring.datasource.username=root spring.datasource.password=123456 spring.datasource.driver-class-name=com.mysql.jdbc.Driver spring.datasource.max-active=10 spring.datasource.max-idle=5 spring.datasource.min-idle=0 四、Mapper的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.dao.PersonDao"> <!-- 根据ID查询数据 --> <select id="findAll" parameterType="String" resultType="com.entity.Person"> select * from Person </select> </mapper> 与普通的mybatis配置一样，只是小心：

1、mapper的命名空间（namespace），一定是所对应的接口的包名+类名

2、parameterType和resultMap，与实际匹配

五、接口文件

package com.dao; import java.util.List; import com.entity.Person; public interface PersonDao { public List<Person>findAll(); } 可以运行跑下了...