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JNDI：Java Naming and Directory Interface(Java命名和目录接口)

一、在webapp下新建META-INF文件夹，再在META-INF下新建context.xml：

Tomcat就会自动检索到该文件，并执行相关操作。

关于context.xml的说明：

1、name可以自定义，比如 name = "mysql"， name = "jdbc/mysql/ssm"都行！

2、driverClassName，这个叫法得记一下！

二、MyBatis主配置文件：

三、使用示例(index.jsp)：

<%@ page import="java.io.InputStream" %><%@ page import="org.apache.ibatis.io.Resources" %><%@ page import="org.apache.ibatis.session.SqlSessionFactory" %><%@ page import="org.apache.ibatis.session.SqlSessionFactoryBuilder" %><%@ page import="org.apache.ibatis.session.SqlSession" %><%@ page import="cn.liuxingchang.dao.RoleDao" %><%@ page import="cn.liuxingchang.domain.User" %><%@ page import="cn.liuxingchang.dao.UserDao" %><%@ page import="java.util.List" %><%@ page import="cn.liuxingchang.domain.Role" %><%@ page contentType="text/html;charset=UTF-8" language="java" %>
Hello World!
<%    InputStream in = Resources.getResourceAsStream("mybatis.xml");    SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);    SqlSession sqlSession = factory.openSession();    RoleDao roleDao = sqlSession.getMapper(RoleDao.class);    UserDao userDao = sqlSession.getMapper(UserDao.class);    List
   
     users = userDao.findAll();    List
    
      roles = roleDao.findAll();    for(User user: users)        System.out.println(user);    for(Role role: roles)        System.out.println(role);    sqlSession.close();    in.close();%>
    
   

说明：

1、要有Web容器。

2、必须经过Web容器，不和Web打交道的Java文件(比如普通的测试类)因为没经过Web容器，所以用不了JNDI类型的数据源。

最后附上源码：

项目结构：

pom.xml:

   
     
    
     4.0.0
      
    
     org.example
      
    
     P077_JNDI
      
    
     1.0-SNAPSHOT
      
    
     war
      
    
     P077_JNDI Maven Webapp
      
      
    
     http://www.example.com
      
        
     
      UTF-8
         
     
      1.7
         
     
      1.7
       
      
        
           
      
       mysql
            
      
       mysql-connector-java
            
      
       8.0.16
          
         
           
      
       org.mybatis
            
      
       mybatis
            
      
       3.4.5
          
       
      
        
     
      P077_JNDI
         
     
            
              
                 
        
         maven-clean-plugin
                  
        
         3.1.0
                
               
               
                 
        
         maven-resources-plugin
                  
        
         3.0.2
                
               
                 
        
         maven-compiler-plugin
                  
        
         3.8.0
                
               
                 
        
         maven-surefire-plugin
                  
        
         2.22.1
                
               
                 
        
         maven-war-plugin
                  
        
         3.2.2
                
               
                 
        
         maven-install-plugin
                  
        
         2.5.2
                
               
                 
        
         maven-deploy-plugin
                  
        
         2.8.2
                
             
          
       
    
   

数据库的相关信息：

MySQL：8.0.16    port：3306    database：multi_table

account表：

user表：

web.xml：无配置

index.jsp:

<%@ page import="java.io.InputStream" %><%@ page import="org.apache.ibatis.io.Resources" %><%@ page import="org.apache.ibatis.session.SqlSessionFactory" %><%@ page import="org.apache.ibatis.session.SqlSessionFactoryBuilder" %><%@ page import="org.apache.ibatis.session.SqlSession" %><%@ page import="cn.liuxingchang.dao.RoleDao" %><%@ page import="cn.liuxingchang.domain.User" %><%@ page import="cn.liuxingchang.dao.UserDao" %><%@ page import="java.util.List" %><%@ page import="cn.liuxingchang.domain.Role" %><%@ page contentType="text/html;charset=UTF-8" language="java" %>
Hello World!
<%    InputStream in = Resources.getResourceAsStream("mybatis.xml");    SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);    SqlSession sqlSession = factory.openSession();    RoleDao roleDao = sqlSession.getMapper(RoleDao.class);    UserDao userDao = sqlSession.getMapper(UserDao.class);    List
   
     users = userDao.findAll();    List
    
      roles = roleDao.findAll();    for(User user: users)        System.out.println(user);    for(Role role: roles)        System.out.println(role);    sqlSession.close();    in.close();%>
    
   

User类：

package cn.liuxingchang.domain;import java.io.Serializable;import java.util.List;public class User implements Serializable {    private Integer id;    private String name;    private Integer age;    private List
   
     roles;    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Integer getAge() {        return age;    }    public void setAge(Integer age) {        this.age = age;    }    public List
    
      getRoles() {        return roles;    }    public void setRoles(List
     
       roles) {        this.roles = roles;    }    @Override    public String toString() {        return "User{" +                "id=" + id +                ", name='" + name + '\'' +                ", age=" + age +                ", roles=" + roles +                '}';    }}
     
    
   

Role类：

package cn.liuxingchang.domain;import java.io.Serializable;import java.util.List;public class Role implements Serializable {    private Integer id;    private String role;    private String info;    private List
   
     users;    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = id;    }    public String getRole() {        return role;    }    public void setRole(String role) {        this.role = role;    }    public String getInfo() {        return info;    }    public void setInfo(String info) {        this.info = info;    }    public List
    
      getUsers() {        return users;    }    public void setUsers(List
     
       users) {        this.users = users;    }    @Override    public String toString() {        return "Role{" +                "id=" + id +                ", role='" + role + '\'' +                ", info='" + info + '\'' +                ", users=" + users +                '}';    }}
     
    
   

UserDao接口：

package cn.liuxingchang.dao;import cn.liuxingchang.domain.User;import java.util.List;public interface UserDao {    List
   
     findAll();}
   

RoleDao接口：

package cn.liuxingchang.dao;import cn.liuxingchang.domain.Role;import java.util.List;public interface RoleDao {    List
   
     findAll();}
   

UserMapper.xml：

   
       
            
             
             
             
                 
                  
                  
              
         
        
            select u.*, r.id as rid, role, info from user u left outer join user_role ur on u.id = ur.uid         left outer join role r on ur.rid = r.id    
   

RoleMapper.xml:

   
       
            
             
             
             
                 
                  
                  
              
         
        
            select r.*, u.id as uid, name, age from role r left outer join user_role ur on r.id = ur.rid          left outer join user u on ur.uid = u.id    
   

context.xml:

mybatis.xml:

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