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:
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:
<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:
<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/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:
DROP TABLE IF EXISTS `tt_user`;
CREATE TABLE `tt_user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`age` int(11) DEFAULT NULL,
`name` varchar(255) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT 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:
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:
public interface UserDao {
public User getUserById(int id);
public int 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:
public class User {
private int id;
private int age;
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getName() {
return name;
}
public void 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:
public interface UserService {
public User getUserById(int id);
public int getUserCount();
}
接口实现如下:
public class UserServiceImpl implements UserService {
@Resource(name = "userDao")
private UserDao userDao;
public User getUserById(int id){
return userDao.getUserById(id);
}
public int getUserCount(){
return userDao.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:
<?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:
<?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:
<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/context http://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>
<bean class="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:
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")
private UserService userService;
@RequestMapping(value = "/userinfo/{id}",method = RequestMethod.GET)
public String showUserInfo(@PathVariable int 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)
public String showHome(ModelMap model){
int count = userService.getUserCount();
model.addAttribute("count",count);
return "count";
}
}
通过浏览器访问页面,即可输出内容: