Mybatis、Maven、Spring、struts2结合使用详解

 Mybatis 与 maven、Spring、struts2 结合使用

首先通过maven的pom.xml文件来导入所需要的jar包，采用的spring4、struts2、maven 和 mybatis3.2。

步骤如下执行。

一、maven 的pom.xml配置文件所需内容

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<dependencies>

        <dependency>

            <groupId>junit</groupId>

            <artifactId>junit</artifactId>

            <version>3.8.1</version>

            <scope>test</scope>

        </dependency>

        <dependency>

            <groupId>org.apache.struts.xwork</groupId>

            <artifactId>xwork-core</artifactId>

            <version>2.3.16.2</version>

        </dependency>

        <dependency>

            <groupId>commons-beanutils</groupId>

            <artifactId>commons-beanutils-core</artifactId>

            <version>1.8.3</version>

        </dependency>

        <dependency>

            <groupId>commons-collections</groupId>

            <artifactId>commons-collections</artifactId>

            <version>20040616</version>

        </dependency>

        <dependency>

            <groupId>commons-fileupload</groupId>

            <artifactId>commons-fileupload</artifactId>

            <version>1.2.2</version>

        </dependency>

        <dependency>

            <groupId>commons-io</groupId>

            <artifactId>commons-io</artifactId>

            <version>2.0.1</version>

        </dependency>

        <dependency>

            <groupId>commons-i18n</groupId>

            <artifactId>commons-i18n</artifactId>

            <version>0.5</version>

            <type>zip</type>

        </dependency>

        <dependency>

            <groupId>javax.servlet</groupId>

            <artifactId>servlet-api</artifactId>

            <version>3.0-alpha-1</version>

        </dependency>

        <dependency>

            <groupId>org.aspectj</groupId>

            <artifactId>aspectjweaver</artifactId>

            <version>1.7.1</version>

        </dependency>

        <dependency>

            <groupId>com.sun</groupId>

            <artifactId>tools</artifactId>

            <version>1.5.0</version>

            <scope>system</scope>

            <systemPath>D:\Program Files\java\jre\lib\rt.jar</systemPath>

        </dependency>

  

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-core</artifactId>

            <version>4.0.4.RELEASE</version>

        </dependency>

        <dependency>

            <groupId>org.hibernate</groupId>

            <artifactId>hibernate-core</artifactId>

            <version>4.3.5.Final</version>

        </dependency>

        <dependency>

            <groupId>org.hibernate</groupId>

            <artifactId>hibernate-c3p0</artifactId>

            <version>4.3.5.Final</version>

        </dependency>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-web</artifactId>

            <version>4.0.4.RELEASE</version>

        </dependency>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-tx</artifactId>

            <version>4.0.4.RELEASE</version>

        </dependency>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-jdbc</artifactId>

            <version>4.0.4.RELEASE</version>

        </dependency>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-orm</artifactId>

            <version>4.0.4.RELEASE</version>

        </dependency>

        <dependency>

            <groupId>org.apache.struts</groupId>

            <artifactId>struts2-core</artifactId>

            <version>2.3.16.2</version>

        </dependency>

        <dependency>

            <groupId>org.apache.struts</groupId>

            <artifactId>struts2-dojo-plugin</artifactId>

            <version>2.3.16.2</version>

        </dependency>

        <dependency>

            <groupId>org.apache.struts</groupId>

            <artifactId>struts2-json-plugin</artifactId>

            <version>2.3.16.2</version>

        </dependency>

        <dependency>

            <groupId>org.apache.struts</groupId>

            <artifactId>struts2-spring-plugin</artifactId>

            <version>2.3.16.2</version>

        </dependency>

        <dependency>

            <groupId>org.apache.logging.log4j</groupId>

            <artifactId>log4j-core</artifactId>

            <version>2.0-beta8</version>

        </dependency>

        <dependency>

            <groupId>org.slf4j</groupId>

            <artifactId>jcl-over-slf4j</artifactId>

            <version>1.7.7</version>

        </dependency>

        <dependency>

            <groupId>org.slf4j</groupId>

            <artifactId>slf4j-api</artifactId>

            <version>1.7.7</version>

        </dependency>

        <dependency>

            <groupId>org.slf4j</groupId>

            <artifactId>slf4j-log4j12</artifactId>

            <version>1.7.7</version>

        </dependency>

        <dependency>

            <groupId>org.freemarker</groupId>

            <artifactId>freemarker</artifactId>

            <version>2.3.23</version>

        </dependency>

        <!-- mybatis jar -->

        <dependency>

            <groupId>org.mybatis</groupId>

            <artifactId>mybatis</artifactId>

            <version>3.2.4</version>

        </dependency>

        <!-- mybatis-spring jar -->

        <dependency>

            <groupId>org.mybatis</groupId>

            <artifactId>mybatis-spring</artifactId>

            <version>1.2.2</version>

        </dependency>

        <!-- <dependency> <groupId>org.apache.ibatis</groupId> <artifactId>ibatis-sqlmap</artifactId> 

            <version>2.3.4.726</version> <scope>compile</scope> </dependency> <dependency> 

            <groupId>jetty</groupId> <artifactId>servlet-api</artifactId> <version>2.5-6.0.2</version> 

            </dependency> -->

        <!-- mysql-connector-java jar -->

        <dependency>

            <groupId>mysql</groupId>

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

            <version>5.1.28</version>

        </dependency>

        <dependency>

            <groupId>cglib</groupId>

            <artifactId>cglib</artifactId>

            <version>2.2.2</version>

        </dependency>

 </dependencies>

二、web.xml配置

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<filter>

        <filter-name>struts2</filter-name>

        <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>

    </filter>

    <filter-mapping>

        <filter-name>struts2</filter-name>

        <url-pattern>/*</url-pattern>

    </filter-mapping>

  

    <listener>

        <description>Spring读取配置文件的监听器</description>

        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>

    </listener>

    <listener>

        <description>Spring防止内存泄漏的监听器</description>

        <listener-class>

            org.springframework.web.util.IntrospectorCleanupListener</listener-class>

    </listener>

  

    <servlet>

        <servlet-name>JspSupportServlet</servlet-name>

        <servlet-class>org.apache.struts2.views.JspSupportServlet</servlet-class>

        <load-on-startup>1</load-on-startup>

    </servlet>

  

    <context-param>

        <param-name>contextConfigLocation</param-name>

        <param-value>

            classpath*:/applicationContext.xml

        </param-value>

    </context-param>

  

    <!-- #字符编码 -->

    <filter>

        <filter-name>encodingFilter</filter-name>

        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>

        <init-param>

            <param-name>encoding</param-name>

            <param-value>UTF-8</param-value>

        </init-param>

        <!-- forceEncoding这个参数,把它设置为true表示不管请求中的编码是什么格式,都

将强制采用encoding中设置的编码方式 -->

        <init-param>

            <param-name>forceEncoding</param-name>

            <param-value>true</param-value>

        </init-param>

    </filter>

  

    <filter-mapping>

        <filter-name>encodingFilter</filter-name>

        <url-pattern>/*</url-pattern>

    </filter-mapping>

  

    <session-config>

        <session-timeout>30</session-timeout>

    </session-config>

三、spring配置

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<!-- 开启注解方式注入 bean -->

    <context:annotation-config />

    <context:component-scan base-package="census"></context:component-scan>

  

    <!-- 读取 properties 配置信息 -->

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

  

    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">

        <!-- 配置数据源 -->

        <property name="driverClass" value="${jdbc.driverClass}"></property>

        <property name="jdbcUrl" value="${jdbc.url}"></property>

        <property name="user" value="${jdbc.user}"></property>

        <property name="password" value="${jdbc.password}"></property>

  

        <!-- 配置 c3p0 数据库连接池 -->

  

        <!--连接池中保留的最小连接数 -->

        <property name="minPoolSize" value="5"></property>

  

        <!--连接池中保留的最大连接数。Default: 15 -->

        <property name="maxPoolSize" value="30"></property>

  

        <!--初始化时获取的连接数，取值应在minPoolSize与maxPoolSize之间。Default: 3 -->

        <property name="initialPoolSize" value="10"></property>

  

        <!--最大空闲时间,1200秒内未使用则连接被丢弃。若为0则永不丢弃。Default: 0 -->

        <property name="maxIdleTime" value="60"></property>

  

        <!--当连接池中的连接耗尽的时候c3p0一次同时获取的连接数。Default: 3 -->

        <property name="acquireIncrement" value="5"></property>

  

        <!--JDBC的标准参数，用以控制数据源内加载的PreparedStatements数量。

 但由于预缓存的statements 属于单个connection而不是整个连接池。 

            所以设置这个参数需要考虑到多方面的因素。如果maxStatements与

 maxStatementsPerConnection均为0，则缓存被关闭。Default: 

            0 -->

        <property name="maxStatements" value="50"></property>

  

        <!--每60秒检查所有连接池中的空闲连接。Default: 0 -->

        <property name="idleConnectionTestPeriod" value="60"></property>

  

        <!--定义在从数据库获取新连接失败后重复尝试的次数。Default: 30 -->

        <property name="acquireRetryAttempts" value="30"></property>

  

        <!--获取连接失败将会引起所有等待连接池来获取连接的线程抛出异常。 

但是数据源仍有效 保留，并在下次调用getConnection()的时候继续尝试获取连接。 

            如果设为true，那么在尝试获取连接失败后该数据源将申明已断开并永久关闭。

Default: false -->

        <property name="breakAfterAcquireFailure" value="false"></property>

  

        <property name="debugUnreturnedConnectionStackTraces">

            <value>true</value>

        </property>

    </bean>

  

    <!-- 创建SqlSessionFactory，并指定数据源 -->

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

        <!--configLocation属性指定mybatis的核心配置文件 -->

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

        <!--dataSource属性指定要用到的连接池 -->

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

        <!-- 映射文件 -->

        <!-- <property name="mapperLocations" value="classpath:sqlmap/*.xml"></property> -->

    </bean>

    <bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">         

       <constructor-arg index="0" ref="sqlSessionFactoryBean" /> 

    </bean>

<!--   

    <bean abstract="true" id="baseDao" class="census.base.BaseDao">

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

    </bean> -->

    <!-- 

    <bean id="userDao" class="census.dao.UserDao" parent="baseDao"></bean> -->

      

    <bean

        class="org.springframework.context.annotation.CommonAnnotationBeanPostProcessor" />

</beans>

四、mybatis的config配置文件

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

<!DOCTYPE configuration

  PUBLIC "-//mybatis.org//DTDConfig 3.0//EN"

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

<configuration>

    <typeAliases>

        <typeAlias type="census.model.User" alias="user"/>

    </typeAliases>

    <mappers>

        <mapper resource="sqlmap/sqlmap-user.xml"/>

    </mappers>

</configuration>

五、mybatis 映射mapper文件配置

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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="User">

    <resultMap type="user" id="userMap">

        <id property="uid" column="id" />

        <result property="name" column="name" />

        <result property="age" column="age" />

    </resultMap> 

      

      

    <select id="getUser" parameterType="user" resultMap="userMap">

        select * from

        t_user where id=#{uid}

    </select>

      

    <select id="getUserList" resultMap="userMap">

        select * from t_user

    </select>

      

      

</mapper>

六、struts 配置

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<!DOCTYPE struts PUBLIC

"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"

"http://struts.apache.org/dtds/struts-2.0.dtd">

  

<struts>

    <constant name="struts.enable.DynamicMethodInvocation" value="true" />

    <constant name="struts.devMode" value="false" />

      

    <package name="default" namespace="/" extends="struts-default">

        <action name="emp-*" class="census.action.UserAction" method="{1}">

            <result name="{1}">/population/census/view/emp-{1}.jsp</result>

        </action>

    </package>

</struts>

七、BaseDao 的代码

因为采用 Mybatis 的这种配置方式，DAO 层都需要SqlSessionTemplate sqlSession ，因此可以写一个BaseDao来存放公共的属性值。

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import org.mybatis.spring.SqlSessionTemplate;

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

  

public class BaseDao<T>{

    @Autowired //该注解是将sqlsession 注入，必需

    public SqlSessionTemplate sqlSession;

      

    public void setSqlSession(SqlSessionTemplate sqlSession) {

        this.sqlSession = sqlSession;

    }

}

八、Dao 层代码

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import org.springframework.stereotype.Repository;

  

import census.base.BaseDao;

import census.model.User;

  

@Repository //该注解是为了让子类 UserDao 的父类 BaseDao 的 sqlsession 不为null

public class UserDao extends BaseDao<User>{

    public User getUser(Integer id){

        return (User) sqlSession.selectOne("User.getUser", id);

    }

}

serviceImpl通过spring 注解注入的方式调用DAO，Action同理

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@Autowired

private UserDao userDao;

九、常见问题

问题1:

Causedby: org.springframework.beans.factory.BeanCreationException:Couldnot autowire field: 
com.uni2uni.service.impl.AuthorityServiceImpl 
com.uni2uni.controller.AdminController.authorityServiceImpl;
nested exception is org.springframework.beans.factory.BeanCreationException:Error creating bean with name 'authorityServiceImpl':
Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: 
Couldnot autowire field:private org.mybatis.spring.SqlSessionTemplate com.uni2uni.service.impl.AuthorityServiceImpl.session; 
nested exception is org.springframework.beans.factory.BeanCreationException:Error creating bean with name 'sqlSessionTemplate'
definedinclass path resource [applicationContext.xml]:Cannot resolve reference to bean 'sqlSessionFactory'while setting
 constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException:Error creating bean with name
'sqlSessionFactory'definedinclass path resource [applicationContext.xml]:Invocation of init method failed; nested exception
is org.springframework.core.NestedIOException:Failed to parse mapping resource:'file [D:\Workspaces\liying\webapp\target\webapp\WEB-INF\
classes\mybatis\tb_admin.xml]'; nested exception is org.apache.ibatis.builder.BuilderException:Error parsing Mapper XML.
Cause: java.lang.IllegalArgumentException:MappedStatements collection already contains value forAdmin.resetAdminPassword
遇到这个问题通常原因有两种：
① 相同的命名空间有相同的 id；
② sqlSessionFactory 中配置了多个 xml 的地址
第一种查 Spring 的配置文件，是否有 Bean 的ID 相同
第二种情况应该是在 Spring 配置MyBatis 的配置信息可能写成这样：
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<!-- 创建SqlSessionFactory，并指定数据源 -->
<bean id="sqlSessionFactoryBean" class="org.mybatis.spring.SqlSessionFactoryBean">
    <!--configLocation属性指定mybatis的核心配置文件 -->
    <property name="configLocation" value="classpath:sqlmap-config.xml"></property>
    <!--dataSource属性指定要用到的连接池 -->
    <property name="dataSource" ref="dataSource"></property>
    <!-- 映射文件 -->
    <property name="mapperLocations" value="classpath:sqlmap/*.xml"></property>
</bean>

这里红色标注的地方与 Mybatis congfig配置文件中的

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<mappers>

    <mapper resource="sqlmap/sqlmap-user.xml"/>

</mappers>

冲突导致，所以可以把Spring的那块代码去掉，或者将 Mybatis config配置文件中的mappers去掉。

问题2:

java.lang.NullPointerException

    at census.dao.UserDao.getUserList(UserDao.java:17)

    at census.service.impl.UserServiceImpl.getUserList(UserServiceImpl.java:22)

    at census.action.UserAction.list(UserAction.java:47)

    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)

    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)

    at java.lang.reflect.Method.invoke(Unknown Source)

    at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:450)

    at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:289)

    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:252)

    at org.apache.struts2.interceptor.DeprecationInterceptor.intercept(DeprecationInterceptor.java:41)

问题的原因是 DAO 层的 sqlSession 为null，解决办法

① 在Spring 配置文件中加上

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<bean abstract="true" id="baseDao" class="census.base.BaseDao">

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

</bean>

<bean id="userDao" class="census.dao.UserDao" parent="baseDao"></bean>

这种解决办法较为麻烦，如果有很多 Dao 的话，就会写很多的 bean。所以不方便。可以采用以下办法

②在 BaseDao 的public SqlSessionTemplate sqlSession; 上方加@Autowired注解，这样就不会再出现ase

空指针异常，另外也要在 BaseDao 的子类类名上方加上@Repository注解。用于 bean 注入。

 

声明：因为本人刚刚学习Mybatis,尝试性的做了第一个测试，如果本博文有错误或者不足之处，请大家留言指出。谢谢..

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