Spring整合MyBatis案例练习笔记

需求:

　用户登录

技术需求:

　　Servlet+Spring+Mybatis+MVC+jsp+css+html+jquery

数据库设计:

　　用户表

Sql语句设计:

　　select * from t_user where uname=#{0} and pwd=#{1}

实现:

　　mapper层

package com.bjsxt.mapper;

import com.bjsxt.pojo.User;

public interface UserMapper {
    //用户登录
    User selUser(String uname,String pwd);
}

　　UserMapper.xml

<?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.bjsxt.mapper.UserMapper">
    <!-- 用户登录sql配置 -->
      <select id="selUser" resultType="com.bjsxt.pojo.User">
          select * from t_user where uname=#{arg0} and pwd=#{arg1}
      </select>
  </mapper>

　　pojo层

package com.bjsxt.pojo;
/**
 * 用户实体类
 * @author Yancy
 *
 */
public class User {
    private int uid;//用户ID
    private String uname;//用户名称
    private String pwd;//用户密码
    public int getUid() {
        return uid;
    }
    public void setUid(int uid) {
        this.uid = uid;
    }
    public String getUname() {
        return uname;
    }
    public void setUname(String uname) {
        this.uname = uname;
    }
    public String getPwd() {
        return pwd;
    }
    public void setPwd(String pwd) {
        this.pwd = pwd;
    }
    public User(int uid, String uname, String pwd) {
        super();
        this.uid = uid;
        this.uname = uname;
        this.pwd = pwd;
    }
    @Override
    public String toString() {
        return "User [uid=" + uid + ", uname=" + uname + ", pwd=" + pwd + "]";
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((pwd == null) ? 0 : pwd.hashCode());
        result = prime * result + uid;
        result = prime * result + ((uname == null) ? 0 : uname.hashCode());
        return result;
    }
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        User other = (User) obj;
        if (pwd == null) {
            if (other.pwd != null)
                return false;
        } else if (!pwd.equals(other.pwd))
            return false;
        if (uid != other.uid)
            return false;
        if (uname == null) {
            if (other.uname != null)
                return false;
        } else if (!uname.equals(other.uname))
            return false;
        return true;
    }
    public User() {
        super();
        // TODO Auto-generated constructor stub
    }

}

　　service层

package com.bjsxt.service;

import com.bjsxt.pojo.User;

public interface UserService {
    //用户登录
    User checkUserInfoService(String uname,String pwd);
}

　　service.impl层

package com.bjsxt.service.impl;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.bjsxt.mapper.UserMapper;
import com.bjsxt.pojo.User;
import com.bjsxt.service.UserService;

public class UserServiceImpl implements UserService {
    private UserMapper um;

    public UserMapper getUm() {
        return um;
    }

    public void setUm(UserMapper um) {
        this.um = um;
    }

    //用户登录
    @Override
    public User checkUserInfoService(String uname, String pwd) {
        //使用对象完成数据库操作
        return um.selUser(uname, pwd);

    }

}

　　servlet层

package com.bjsxt.servlet;

import java.io.IOException;

import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

import com.bjsxt.pojo.User;
import com.bjsxt.service.UserService;

public class UserServlet extends HttpServlet{
    UserService us;
    @Override
    public void init() throws ServletException {
        //传统方式
//        //获取Spring容器对象
//        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
//        //获取业务层对象
//        us = (UserService) ac.getBean("us");
        //优化方式
        ApplicationContext ac=WebApplicationContextUtils.getWebApplicationContext(this.getServletContext());
        us = (UserService) ac.getBean("us");
    }
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //请求编码格式
        req.setCharacterEncoding("utf-8");
        //设置响应编码格式
        resp.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;charset=utf-8");
        //获取请求信息
        String uname=req.getParameter("uname");
        String pwd=req.getParameter("pwd");
        //处理请求信息

            //调用方法处理请求
            User u = us.checkUserInfoService(uname, pwd);
        //处理响应结果
            if(u!=null) {
                resp.sendRedirect(req.getContextPath()+"/success.jsp");
            }
    }
}

　　配置文件src目录下

　　applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://www.springframework.org/schema/beans
      http://www.springframework.org/schema/beans/spring-beans-4.2.xsd">
      <!-- 配置数据源 -->
      <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
          <property name="driverClassName" value="com.mysql.jdbc.Driver" />
          <property name="url" value="jdbc:mysql://localhost:3306/mybatis"></property>
          <property name="username" value="root"></property>
          <property name="password" value="123456"></property>
      </bean>
      <!-- 配置工厂bean -->
      <bean id="factory" class="org.mybatis.spring.SqlSessionFactoryBean">
          <property name="dataSource" ref="dataSource"></property>
      </bean>
      <!-- 配置mapper扫描bean -->
      <bean id="mapper" class="org.mybatis.spring.mapper.MapperScannerConfigurer">
          <property name="sqlSessionFactory" ref="factory"></property>
          <property name="basePackage" value="com.bjsxt.mapper"></property>
      </bean>
      <!-- 配置业务层bean -->
      <bean id="us" class="com.bjsxt.service.impl.UserServiceImpl">
          <property name="um" ref="userMapper"></property>
      </bean>

</beans>

log4j.properties

# Global logging configuration
log4j.rootLogger=ERROR, stdout
# MyBatis logging configuration...
log4j.logger.com.bjsxt=DEBUG
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

　　web.xml在WEB-INF下

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" 
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">
  <!-- 配置Spring文件路径 -->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:applicationContext.xml</param-value>
    </context-param>
  <!-- 配置监听器 -->
  <listener>
      <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
  </listener>

  <!-- 配置Servlet -->
  <servlet>
      <servlet-name>user</servlet-name>
      <servlet-class>com.bjsxt.servlet.UserServlet</servlet-class>
      <load-on-startup>1</load-on-startup>

  </servlet>
  <servlet-mapping>
      <servlet-name>user</servlet-name>
      <url-pattern>/user</url-pattern>
  </servlet-mapping>
</web-app>

整合问题及其解决方案:

　　问题一:

　　　　传统方式是在service层直接通过mybatis对象完成数据的操作,业务层和mapper层的耦合性非常高.

　　解决一:

　　　　使用SpringIOC技术和service层和mapper层进行解耦.

　　方案一:

　　　　直接从Spring容器对象中获取Mapper对象

　　　　　　--->Spring容器还管理SqlSession对象

　　　　　　　　--->Spring容器还管理DataSource对象

　　实现一:

　　　　参照配置文件

　　问题二:

　　　　如果在Servlet层中直接new创建业务层对象,虽然可以正常使用,但是会造成Servlet层和业务层的耦合性较高,不易于后期的的迭代升级.

　　解决二:

　　　　使用SpringIOC将Servlet层和service层进行解耦.

　　实现二:

　　　　将Service对象配置成bean,交由Spring容器管理.在Servlet中通过Spring容器对象获取业务层对象

　　问题三:

　　　　我们实现的登录代码,如果放在高并发环境,我们发现Spring容器对象一个线程中会被创建两次,这样造成占据的内存过多.

　　解决三:

　　　　①在service层中我们使用Spring容器对象获取Mapper接口对象,Mapper接口对象本身就在Spring容器中,但是我们把Service也配置成bean了,那么是不是可以使用依赖注入呢.直接在Spring的配置文件中通过依赖注入将Mapper对象注入给service对象

　　　　②使用init方法,将获取us对象的动作放到服务器启动是完成.

　　问题四:

　　　　Spring容器在获取的代码的路径在init方法中耦合性较高.

　　解决四:

　　　　将Spring容器相关路径信息配置到web.xml中

　　实现四:

　　　　在web.xml中配置全局参数表明Spring路径

　　　　配置Spring监听器