Spring集成MyBatis

如果觉得Hibernate不够灵活，可以尝试用Mybatis。相比于Hibernate，Mybatis则显得更加轻量、更加灵活，对于我这种不喜欢被束缚的人，使用Mybatis更加顺手、舒心一些。

MyBatis是什么

MyBatis 是支持定制化 SQL、存储过程以及高级映射的优秀的持久层框架。MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。MyBatis 可以对配置和原生Map使用简单的 XML 或注解，将接口和 Java 的 POJOs(Plain Old Java Objects,普通的 Java对象)映射成数据库中的记录。

项目结构及说明

项目最终结构如下图：

 

项目结构介绍：

• com.springapp.mvc包为mvc结构，分别为视图、数据访问层、模型、服务接口。
• resource中分别放置各种配置文件和属性定义文件
• webapp/WEB-INF/view中为freemarker的模板文件
• mvc-dispatcher-servlet.xml为默认的mvc配置文件
• web.xml是java web项目配置文件

引用MyBatis的支持

之前创建MVC项目的过程不是本文介绍重点，略过不讲。此项目采用maven的方式创建，引用MyBatis非常简单，只需在pom文件中添加如下内容：

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<dependency>

    <groupId>org.mybatis</groupId>

    <artifactId>mybatis</artifactId>

    <version>3.3.0</version>

</dependency>

 

<dependency>

    <groupId>org.mybatis</groupId>

    <artifactId>mybatis-spring</artifactId>

    <version>1.2.3</version>

</dependency> 

除此之外还要包括mysql驱动器包、freemarker等，完整的pom文件配置如下：

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<projectxmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.springapp</groupId>

    <artifactId>springmvc_mybatis</artifactId>

    <packaging>war</packaging>

    <version>1.0-SNAPSHOT</version>

    <name>springmvc_mybatis</name>

 

    <properties>

        <spring.version>4.1.6.RELEASE</spring.version>

    </properties>

 

    <!--Spring mvc -->

    <dependencies>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-core</artifactId>

            <version>${spring.version}</version>

        </dependency>

 

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-web</artifactId>

            <version>${spring.version}</version>

        </dependency>

 

        <dependency>

            <groupId>javax.servlet</groupId>

            <artifactId>servlet-api</artifactId>

            <version>2.5</version>

        </dependency>

 

        <dependency>

            <groupId>javax.servlet.jsp</groupId>

            <artifactId>jsp-api</artifactId>

            <version>2.1</version>

            <scope>provided</scope>

        </dependency>

 

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-webmvc</artifactId>

            <version>${spring.version}</version>

        </dependency>

 

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-test</artifactId>

            <version>${spring.version}</version>

            <scope>test</scope>

        </dependency>

 

        <dependency>

            <groupId>org.freemarker</groupId>

            <artifactId>freemarker</artifactId>

            <version>2.3.23</version>

        </dependency>

 

 

        <!--freemarker依赖此包 -->

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-context-support</artifactId>

            <version>${spring.version}</version>

        </dependency>

 

        <!-- myBatis-->

        <dependency>

            <groupId>org.mybatis</groupId>

            <artifactId>mybatis</artifactId>

            <version>3.3.0</version>

        </dependency>

 

        <dependency>

            <groupId>org.mybatis</groupId>

            <artifactId>mybatis-spring</artifactId>

            <version>1.2.3</version>

        </dependency>

 

        <!-- mysql驱动包 -->

        <dependency>

            <groupId>mysql</groupId>

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

            <version>5.1.29</version>

        </dependency>

 

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-jdbc</artifactId>

            <version>4.2.3.RELEASE</version>

        </dependency>

 

        <dependency>

            <groupId>junit</groupId>

            <artifactId>junit</artifactId>

            <version>4.11</version>

            <scope>test</scope>

        </dependency>

    </dependencies>

 

    <build>

        <finalName>springmvc_mybatis</finalName>

        <plugins>

            <plugin>

                <artifactId>maven-compiler-plugin</artifactId>

                <configuration>

                    <source>1.6</source>

                    <target>1.6</target>

                </configuration>

            </plugin>

            <plugin>

                <artifactId>maven-surefire-plugin</artifactId>

                <configuration>

                    <includes>

                        <include>**/*Tests.java</include>

                    </includes>

                </configuration>

            </plugin>

        </plugins>

    </build>

</project>

如果项目采用非maven方式创建，可下载MyBatis的相关的jar包，引用到项目中。包括mybatis和mybatis-spring这两个jar包，其中mybatis-spring是mybatis对spring的支持。

开始使用MyBatis

创建数据库test，并添加表tt_user,创建表的sql如下：

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DROP TABLE IF EXISTS `tt_user`;

CREATE TABLE `tt_user` (

  `id`int(11) NOTNULL AUTO_INCREMENT,

  `age`int(11) DEFAULTNULL,

  `name`varchar(255) DEFAULT NULL,

  PRIMARYKEY (`id`)

) ENGINE=InnoDB AUTO_INCREMENT=2DEFAULT CHARSET=utf8;　

在resource/conf中添加jdbc配置文件，设置相关属性，属性内容如下：

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jdbc_driverClassName=com.mysql.jdbc.Driver

jdbc_url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8

jdbc_username=root

jdbc_password=root

在dao中添加user的数据访问层接口，内容如下，其中接口定义了getUserById()和getUserCount()两个方法：

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public interface UserDao {

    publicUser getUserById(intid);

 

    publicint getUserCount();

}

在model中添加user的对象模型类，这里定义的字段名和数据库字段名相同，方便MyBatis查询结果和对象实体做映射，不用再定义resultmap：

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public class User {

 

    privateint id;

 

    privateint age;

 

    privateString name;

 

    publicint getId() {

        returnid;

    }

 

    publicvoid setId(intid) {

        this.id = id;

    }

 

    publicint getAge() {

        returnage;

    }

 

    publicvoid setAge(intage) {

        this.age = age;

    }

 

    publicString getName() {

        returnname;

    }

 

    publicvoid setName(String name) {

        this.name = name;

    }

}

在service中定义服务接口和接口实现：

接口定义如下：

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public interface UserService {

    publicUser getUserById(intid);

 

    publicint getUserCount();

}

接口实现如下：

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public class UserServiceImpl implementsUserService {

 

 

    @Resource(name ="userDao")

    privateUserDao userDao;

 

    publicUser getUserById(intid){

        returnuserDao.getUserById(id);

    }

 

    publicint getUserCount(){

        returnuserDao.getUserCount();

    }

}

以上这些定义了关于User对象的一系列mvc层次代码，接下来定义UserMapper文件，此文件是MyBatis中SQL定义文件，需要在此配置文件中定义dao数据访问接口中需要用到的sql语句，本例比较简单只有两个方法，分别是getUserById和getUserCount，命名为UserMapper.xml，并存放在resource/mapper文件夹中，内容如下：

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<?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.springapp.mvc.dao.UserDao">

    <select id="getUserById"resultType="com.springapp.mvc.model.User">

        SELECT * FROM tt_user WHERE id= #{id}

    </select>

 

    <select id="getUserCount"resultType="int">

        SELECT COUNT(*) FROM tt_user

    </select>

</mapper>

其中id为dao数据访问接口中方法名称，resultType为返回值类型，参数需要用#{参数名}表示。

配置mybatis-config，指定mapper文件以及给实体设定别名，在resource/conf文件夹中创建mybatis-config.xml，内容如下：

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<?xml version="1.0"encoding="UTF-8"?>

<!DOCTYPE configuration

        PUBLIC"-//mybatis.org//DTD Config 3.0//EN"

        "http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>

    <!-- 命名空间 设置别名-->

    <typeAliases>

        <typeAlias alias="User"type="com.springapp.mvc.model.User"/>

    </typeAliases>

 

    <!-- 映射map 指定映射文件-->

    <mappers>

        <mapper resource="mapper/UserMapper.xml"></mapper>

    </mappers>

</configuration>

通过设置mappers，设置数据访问接口对应的映射文件，通过设置typeAlias，指定实体模型的别名，例如，这里讲com.springapp.mvc.model.User设置别名为User，那么在UserMapper.xml中，可以将getUserById的resultType直接指定为User,就不需要加包前缀了。

最后，在mvc-dispatcher-servlet.xml中配置相关的bean、freemarker等配置，内容如下：

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<beans xmlns="http://www.springframework.org/schema/beans"

       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

       xmlns:context="http://www.springframework.org/schema/context"

       xsi:schemaLocation="http://www.springframework.org/schema/beans

        http://www.springframework.org/schema/beans/spring-beans.xsd

        http://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsd">

 

    <context:component-scan base-package="com.springapp.mvc"/>

 

    <!-- 导入属性配置文件 -->

    <context:property-placeholder location="classpath:conf/jdbc.properties"/>

 

    <!--配置数据源-->

    <bean id="dataSource"class="org.springframework.jdbc.datasource.DriverManagerDataSource">

        <property name="driverClassName">

            <value>${jdbc_driverClassName}</value>

        </property>

        <property name="url">

            <value>${jdbc_url}</value>

        </property>

        <property name="username">

            <value>${jdbc_username}</value>

        </property>

        <property name="password">

            <value>${jdbc_password}</value>

        </property>

    </bean>

 

    <bean id="transactionManager"class="org.springframework.jdbc.datasource.DataSourceTransactionManager">

        <property name="dataSource"ref="dataSource"/>

    </bean>

 

    <bean id="sqlSessionFactory"class="org.mybatis.spring.SqlSessionFactoryBean">

        <property name="configLocation"value="classpath:conf/mybatis-config.xml"/>

        <property name="dataSource"ref="dataSource"/>

    </bean>

 

    <!-- mapper bean -->

    <bean id="userDao"class="org.mybatis.spring.mapper.MapperFactoryBean">

        <property name="mapperInterface"value="com.springapp.mvc.dao.UserDao"/>

        <property name="sqlSessionFactory"ref="sqlSessionFactory"/>

    </bean>

 

    <bean id="userService"class="com.springapp.mvc.service.impl.UserServiceImpl">

        <!--<property name="userDao"ref="userDao"></property>  若启用此配置 UserServiceImpl类中的userDao必须具有setter和getter-->

    </bean>

 

 

    <!-- freemarker的配置 -->

    <bean id="freemarkerConfigurer"

          class="org.springframework.web.servlet.view.freemarker.FreeMarkerConfigurer">

        <property name="templateLoaderPath"value="/WEB-INF/view/"/>

        <property name="defaultEncoding"value="utf-8"/>

        <property name="freemarkerSettings">

            <props>

                <prop key="template_update_delay">10</prop>

                <prop key="locale">zh_CN</prop>

                <prop key="datetime_format">yyyy-MM-dd HH:mm:ss</prop>

                <prop key="date_format">yyyy-MM-dd</prop>

                <prop key="number_format">#.##</prop>

            </props>

        </property>

    </bean>

    <!-- FreeMarker视图解析 如返回userinfo。。在这里配置后缀名ftl和视图解析器。。 -->

    <bean id="viewResolver"

          class="org.springframework.web.servlet.view.freemarker.FreeMarkerViewResolver">

        <property name="viewClass"

                  value="org.springframework.web.servlet.view.freemarker.FreeMarkerView"/>

        <property name="suffix"value=".ftl"/>

        <property name="contentType"value="text/html;charset=utf-8"/>

        <property name="exposeRequestAttributes"value="true"/>

        <property name="exposeSessionAttributes"value="true"/>

        <property name="exposeSpringMacroHelpers"value="true"/>

    </bean>

 

    <beanclass="org.springframework.web.servlet.view.InternalResourceViewResolver">

        <property name="prefix"value="/WEB-INF/pages/"/>

        <property name="suffix"value=".jsp"/>

    </bean>

 

</beans>

之后在controller中加入视图方法，输出查询内容：

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import com.springapp.mvc.dao.UserDao;

import com.springapp.mvc.model.User;

import com.springapp.mvc.service.UserService;

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

import org.springframework.stereotype.Controller;

import org.springframework.ui.ModelMap;

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

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

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

 

import javax.annotation.Resource;

 

@Controller

@RequestMapping("/restful")

public class HelloController {

 

    @Resource(name ="userService")

    privateUserService userService;

 

    @RequestMapping(value ="/userinfo/{id}",method = RequestMethod.GET)

    publicString showUserInfo(@PathVariableint id, ModelMap model){

        User user = userService.getUserById(id);

        if(user!=null) {

            model.addAttribute("name", user.getName());

        }else{

            model.addAttribute("name","查无此用户");

        }

        return"home";

    }

 

 

 

    @RequestMapping(value ="/home",method = RequestMethod.GET)

    publicString showHome(ModelMap model){

        intcount = userService.getUserCount();

        model.addAttribute("count",count);

        return"count";

    }

}

通过浏览器访问页面，即可输出内容：

　　

demo下载