Mybatis环境搭建

Posted 2021-01-29 xzwu

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一、mybatis环境搭建：

mybatis.jar与mysql.jar,需要在pom.xml中引入这两个jar的依赖

 1     <dependency>
 2       <groupId>org.mybatis</groupId>
 3       <artifactId>mybatis</artifactId>
 4       <version>3.4.6</version>
 5     </dependency>
 6     <dependency>
 7       <groupId>mysql</groupId>
 8       <artifactId>mysql-connector-java</artifactId>
 9       <version>5.1.44</version>
10     </dependency>

mybatis-config.xml---mybatis的主配置文件，包括数据库连接池的配置，映射配置文件路径（类路径下）

 1 <?xml version=‘1.0‘ encoding=‘UTF-8‘?>
 2 <!DOCTYPE configuration
 3         PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
 4         "http://mybatis.org/dtd/mybatis-3-config.dtd">
 5 <configuration>
 6     <properties resource="db.properties"/><!--加载db.properties-->
 7     <environments default="development"> <!--进行数据源的配置，可以配置多个数据源，default属性来配置默认数据源-->
 8         <environment id="development">
 9             <transactionManager type="JDBC"/>
10             <dataSource type="POOLED">
11                 <property name="driver" value="${driver}"/>
12                 <property name="url" value="${url}"/>
13                 <property name="username" value="${username}"/>
14                 <property name="password" value="${password}"/>
15             </dataSource>
16         </environment>
17     </environments>
18     <mappers>
19         <mapper resource="mappers/studentMapper.xml"/>
20     </mappers>
21 </configuration>

db.properties配置（类路径下）

1 driver=com.mysql.jdbc.Driver
2 url=jdbc:mysql://localhost:3306/test?characterEncoding=utf8
3 username=root
4 password=root

log4j.properties配置（类路径下）

1 log4j.rootLogger=DEBUG, A1
2 log4j.appender.A1=org.apache.log4j.ConsoleAppender
3 log4j.appender.A1.layout=org.apache.log4j.PatternLayout
4 log4j.appender.A1.layout.ConversionPattern=%-4r %-5p [%t] %37c %3x - %m%n

外部映射文件配置studentMapper.xml(在mapper文件夹中）

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper
 3         PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 4         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 5 <mapper namespace="com.entity.Student"><!-- 这里是实体类的全路径,namespace用于session级别的缓存管理-->
 6     <resultMap id="forStudent" type="com.entity.Student">
 7         <result column="name" property="name"/>
 8         <result column="id" property="id"/>
 9         <result column="reg_no" property="reg_no"/>
10         <result column="sex" property="sex"/>
11         <result column="age" property="age"/>
12         <result column="grade" property="grade"/>
13         <result column="major" property="major"/>
14 
15         <collection property="listCourse" javaType="ArrayList"
16                     column="major" ofType="com.entity.Course"
17                     select="getCourse">
18         </collection>
19     </resultMap>
20     <select id="getCourse" resultType="com.entity.Course">
21         select * from course where major_name = #{major}
22     </select>
23     <select id="selectAll" resultMap="forStudent" >
24     select * from student
25         <if test="id != null">
26             where id = #{id}
27         </if>
28   </select>
29     <insert id="addStudent" useGeneratedKeys="true" keyProperty="id">
30         insert into student (id,reg_no,name,sex,age,grade,major)
31         values(#{id},#{reg_no},#{name},#{sex},#{age},#{grade},#{major})
32     </insert>
33     <update id="updateStudent">
34         update student set name=#{name},age=#{age},sex=#{sex},grade=#{grade},major=#{major} where id=#{id};
35     </update>
36 </mapper>

二、java中Mybatis执行流程：

加载mybatis-config文件
创建InputStream
获得SqlSessionFactory
获得SqlSession

执行配置好的sql

@org.junit.Test
    public void test1() throws IOException {
        String resource = "mybatis-config.xml"
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        List<Student> list = session.selectList("selectAll");
        System.out.println(list);
        session.close();
    }

三、javaWEB中mybatis执行流程

创建一个SQLSessionFactoryUtils,封装获取SqlSessionFactory的一些方法

 1 public class SqlSessionFactoryUtils {
 2 
 3     private static String RESOURCE = "mybatis-config.xml";
 4 
 5     private static SqlSessionFactory sqlSessionFactory;
 6 
 7     private static ThreadLocal<SqlSession> threadLocal = new ThreadLocal<SqlSession>();
 8 
 9     /**
10      * 创建一个初始化SqlSessionFactory的方法
11      */
12     public static void initSqlSessionFactry() {
13         try {
14             InputStream is = Resources.getResourceAsStream(RESOURCE);
15 
16             sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
17         } catch (IOException e) {
18             e.printStackTrace();
19         }
20     }
21 
22     /**
23      * 获取工厂对象的方法
24      * @return
25      */
26     public static SqlSessionFactory getSqlSessionFactory() {
27         return sqlSessionFactory;
28     }
29 
30     /**
31      * 关闭SqlSession的方法
32      */
33     public static void close(){
34         SqlSession session = threadLocal.get();
35         if(session != null) {
36             session.close();
37             threadLocal.set(null);
38         }
39     }
40 }

创建InitialSqlSessionListener,,当web容器启动时加载SqlSessionFactory,web容器关闭时销毁SqlSessionFactory

@WebListener
public class InitSqlSessionListener implements ServletContextListener {
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        System.out.println("容器加载中...");
        // 初始化我们的SqlSesionFactory对象
        SqlSessionFactoryUtils.initSqlSessionFactry();
    }

    public void contextDestroyed(ServletContextEvent servletContextEvent) {
        System.out.println("容器销毁中...");
        // 关闭SqlSession对象
        SqlSessionFactoryUtils.close();
    }
}

创建StudentDao

 1 public class StudentDao {
 2     public List<Student> selectAll(){
 3         SqlSession session = SqlSessionFactoryUtils.getSqlSessionFactory().openSession();
 4         List<Student> studentList = session.selectList("selectAll");
 5         return studentList;
 6     }
 7     public int addStudent(Student student){
 8         SqlSession session = SqlSessionFactoryUtils.getSqlSessionFactory().openSession();
 9         int result = session.insert("addStudent", student);
10         session.commit();
11         return result;
12     }
13     public void updateStudent(Student student) {
14         SqlSession session = SqlSessionFactoryUtils.getSqlSessionFactory().openSession();
15         session.update("updateStudent",student);
16         session.commit();
17     }
18 
19     public Student selectStuById(int id) {
20         SqlSession session = SqlSessionFactoryUtils.getSqlSessionFactory().openSession();
21         Student stu = new Student();
22         stu.setId(id);
23         Student student = session.selectOne("selectAll",stu);
24         System.out.println(student);
25         return student;
26     }
27 }

创建StudentService(为了方便，省去了)

创建StudentServlet

@WebServlet(value = "/StudentServlet")
public class StudentServlet extends HttpServlet {
    StudentDao dao;
    public StudentServlet(){
        dao = new StudentDao();
    }
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String path = req.getServletPath();
//        if(Objects.equals(path, "/aaaa")){
            List<Student> studentList = dao.selectAll();
        System.out.println(studentList);
            req.setAttribute("studentList", studentList);
            req.getRequestDispatcher("/index.jsp").forward(req, resp);
//        }
    }
}

编写index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>
<html>
<head>
    <title>学生管理系统</title>
    <link rel="stylesheet" href="lib/bootstrap-3.3.7-dist/css/bootstrap.min.css">
    <script src="lib/2.2.4/jquery-1.12.4.min.js"></script>
    <script src="lib/bootstrap-3.3.7-dist/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
    <div class="row">
        <div class="page-header">
            <h1>学生后台管理系统 <small>学生数据管理中心</small></h1>
        </div>
    </div>
    <div class="row">
        <div class="jumbotron">
            <h1>学生管理系统</h1>
            <p>对学生信息进行增删改查</p>
            <p><a class="btn btn-primary btn-lg" href="#" role="button">查看更多</a></p>
            <p><a class="btn btn-primary btn-lg" href="${pageContext.request.contextPath}/addStudent.jsp" role="button">添加学生</a></p>
        </div>
    </div>
    <div class="row">
        <table class="table table-hover table-striped">
            <tr>
                <th>用户编号</th>
                <th>学号</th>
                <th>姓名</th>
                <th>年龄</th>
                <th>性别</th>
                <th>年级</th>
                <th>专业</th>
                <th>操作</th>
            </tr>
            <c:forEach var="student"  items="${studentList}">
            <tr>
                <td>${student.id}</td>
                <%--<td>${user.username}</td>--%>
                <td>${student.reg_no}</td>
                <td>${student.name}</td>
                <td>${student.age}</td>
                <td>${student.sex}</td>
                <td>${student.grade}</td>
                <td>${student.major}</td>
                <td><a href="SelectStudentById?id=${student.id}">查看</a></td>
            </tr>
            </c:forEach>
        </table>
    </div>
</div>
</body>
</html>
<!--
-->

测试

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