MyBatis配置文件的写法和简单使用

<?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>  <typeAliases>  <!-- 配置类型的别名 -->  <typeAlias alias="User" type="cn.hncu.domain.User" />  </typeAliases>  <environments default="development">  <environment id="development">   <transactionManager type="JDBC" />   <dataSource type="POOLED">   <property name="driver" value="com.mysql.jdbc.Driver" />   <property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis?characterEncoding=UTF-8" />   <property name="username" value="hncu" />   <property name="password" value="1234" />   <property name="poolMaximumActiveConnections" value="5"/>   </dataSource>  </environment>  </environments>  <mappers>  <mapper resource="cn/hncu/domain/User.xml"></mapper>  <mapper resource="cn/hncu/domain/User2.xml"></mapper>  </mappers> </configuration> 

package cn.hncu.utils; import java.io.IOException; import java.io.InputStream; import java.sql.Connection; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import com.mysql.jdbc.interceptors.SessionAssociationInterceptor; public class SqlSessionUtils {  private static SqlSessionFactory sessionFactory=null;//DataSource--pool  static{  try {   InputStream in=Resources.getResourceAsStream("mybatis-config.xml");//加载配置文件   sessionFactory=new SqlSessionFactoryBuilder().build(in);   /*   * 这里给出一种不需要使用Resources类加载文件的方法(利用ClassLoader以底层加载配置文件)   sessionFactory=new SqlSessionFactoryBuilder().build(SqlSessionUtils.class.getClassLoader().getResourceAsStream("mybatis-config.xml"));   */  } catch (IOException e) {   e.printStackTrace();  }  }  public static SqlSessionFactory getSessionFactory(){  return sessionFactory;  }  public static SqlSession getSqlSession(){  return sessionFactory.openSession();  }  public static void main(String[] args) {  //mybatis在池中控制的是连接的数量  for(int i=0;i<10;i++){   SqlSession s=getSqlSession();   System.out.println(s);   Connection con=s.getConnection();   System.out.println("con: "+con);  }  } } 

package cn.hncu.domain; public class User {  private String id;  private String name;  private String pwd;  public String getId() {  return id;  }  public void setId(String id) {  this.id = id;  }  public String getName() {  return name;  }  public void setName(String name) {  this.name = name;  }  public String getPwd() {  return pwd;  }  public void setPwd(String pwd) {  this.pwd = pwd;  }  @Override  public String toString() {  return "User [id=" + id + ", name=" + name + ", pwd=" + pwd + "]";  } }

<?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="users">  <select id="all" resultType="cn.hncu.domain.User">  select * from users  </select> </mapper> 

package cn.hncu.domain; import java.util.List; public interface UserMapper {  public List<User> all();  public List<User> user2(String string);  public List<User> user3(User user); } 

package cn.hncu.demo; import java.util.HashMap; import java.util.List; import java.util.Map; import org.apache.ibatis.session.SqlSession; import org.junit.Test; import cn.hncu.domain.User; import cn.hncu.domain.UserMapper; import cn.hncu.utils.SqlSessionUtils; public class Demo1 {  @Test  public void test1(){  //先获取SqlSession  SqlSession s=SqlSessionUtils.getSqlSession();  List<User> list=s.selectList("users.all");//返回结果用list封装，参数用id来指定使用映射文件中的哪一段，<select>或<insert>等sql操作 // List<User> list=s.selectList("all");//省略命名空间----如果名称(id)冲突，则必须使用命名空间来进行识别  //System.out.println(list);  for(User u:list){   System.out.println(u);  }  }  <span style="color:#ff0000;">//使用接口方式操作数据库(推荐使用这种方式，更安全)  /*步骤  * 1.写一个接口:UserMapper，接口中的抽象方法名必须和<select>的属性id值相同，即一个抽象方法代表一段操作  * 2.把User2.xml中的命名空间改成接口的完全类名  * 3.在测试代码中(又dao层的java)，用"s.getMapper()"获得一个代理类对象，使用该对象调用某个方法，即执行某段操作  */</span>  @Test//面向接口的方式，以下调用的都是: User2.xml  public void test2(){  //先获取SqlSession  SqlSession s=SqlSessionUtils.getSqlSession();  UserMapper m=s.getMapper(UserMapper.class);//获得一个代理对象  List<User>list=m.all();  System.out.println(list);  }  ///////////////test3()演示条件查询中的单条件查询,调用User2.xml///////////////////  @Test//传统方式  public void test3_1(){  SqlSession s=SqlSessionUtils.getSqlSession(); // List<User> users=s.selectList("cn.hncu.domain.UserMapper.all");  List<User> users=s.selectList("user2","2");//返回结果用List封装，内部的元素文件类型由映射文件配置  System.out.println(users);  }  @Test//面向接口方式  public void test3_2(){  SqlSession s=SqlSessionUtils.getSqlSession();  UserMapper u=s.getMapper(UserMapper.class);  List<User> users=u.user2("3");  System.out.println(users);  }  ///////////////////多条件查询(条件查询最好用对象封装条件)//////////////  @Test  public void test4(){  SqlSession s=SqlSessionUtils.getSqlSession();  UserMapper u=s.getMapper(UserMapper.class);  User user=new User();  user.setId("4");  user.setName("二蛋");  List<User> users=u.user3(user);  System.out.println(users);  }  @Test  public void test5(){//返回结果用map  SqlSession s=SqlSessionUtils.getSqlSession();  System.out.println(s);  List<Map<String,Object>> users=s.selectList("user4");  for(Map<String,Object> user:users){   System.out.println(user);  }  }  @Test//把输入参数设为map  public void test6(){  SqlSession s=SqlSessionUtils.getSqlSession();  Map<String, Object> map=new HashMap<String,Object>();  map.put("id", "5");  map.put("name", "小奇");  List<Map<String,Object>> users=s.selectList("user5",map);  for(Map<String,Object> user:users){   System.out.println(user);  }  } } 

<?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"> <!-- 当前配置文件专用展示面向接口的操作方式 --> <!-- <mapper namespace="cn.hncu.domain.UserMapper">  <select id="all" resultType="cn.hncu.domain.User">  select * from users  </select> </mapper> --> <mapper namespace="cn.hncu.domain.UserMapper"> <!-- 使用了类型别名 -->  <select id="all" resultType="User">  select * from users  </select>  <!--条件查询之单条件查询，下面的sql语句的参数可以随便写 -->  <select id="user2" resultType="User" parameterType="string">  select * from users where id=#{xx}  </select>  <!--条件查询之多条件查询，下面的sql语句的参数必须要和值对象的属性名一致(要用if条件式判断参数是否为空) -->  <select id="user3" resultType="User" parameterType="string">  select * from users where id=#{id}  <if test="name!=null">   and name=#{name}  </if>  </select>  <!-- 把查询结果封装成List<Map<>> -->  <select id="user4" resultType="map">  select * from users  </select>  <!-- 把输入参数封装成map类型 -->  <select id="user5" resultType="hashmap" parameterType="hashmap">  select * from users where id=#{id}  <if test="name!=null">   and name=#{name}  </if>  </select> </mapper>