独立出properties的mybatis连接池

 jdbc.driver=com.mysql.jdbc.Driver
 jdbc.url=jdbc:mysql://localhost:3306/java505?useSSL=true&characterEncoding=utf8&useSSL=true
 jdbc.username=root
 jdbc.password=root

 <?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>
       <properties resource="db.properties"/>
       <!-- 用于指定使用哪个开发
                                 用于指定使用的环境id
        -->
       <environments default="dev">
           <!-- 用于配置开发环境
                id：环境的唯一识别码
            -->
           <environment id="dev">
               <!-- 事务管理器
                    type：用于设定mybatis采用什么方式管理事务
                    JDBC表示和JDBC一样事务的管理方式
                -->
               <transactionManager type="JDBC"/>
               <!-- 数据源/连接池
                                                          用于配置链接池和数据库链接的参数
                    type：用于设置mybatis是否采用链接池技术
                                                         连接池：用来存数据库链接的，减少数据库的频繁开关
                    POOLED表示mybatis采用连接池技术
                -->
               <dataSource type="POOLED">
                   <property name="driver" value="${jdbc.driver}"/>
                   <property name="url" value="${jdbc.url}"/>
                   <property name="username" value="${jdbc.username}"/>
                   <property name="password" value="${jdbc.password}"/>
               </dataSource>
           </environment>
       </environments>
       <!-- 扫描mapper文件 -->
       <!-- 文件的全限制路径要用/ -->
       <mappers>
           <mapper resource="com/bjsxt/mapper/UserMapper.xml"/>
       </mappers>
   </configuration>

 <?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">
   <!-- namespa：命名空间，可以随意定义，一般情况下要写全限定路径（包名加类）
        MyBatis管理SQL语句是通过namespace+id来定位的
    -->
 <mapper namespace="com.bjsxt.mapper.UserMapper">
     <!-- select标签用于编写查询语句
          id:sql语句的唯一的标识，类比为方法名
          resultType：用于设定返回结果的类型(全限定路径)
          如果返回结果是集合，要写集合泛型的类型
      -->
     <select id="sellAll" resultType="com.bjsxt.pojo.User">
         select * from t_user
     </select>
     <select id="selOne" resultType="com.bjsxt.pojo.User">
         select * from t_user where id=1
     </select>
 </mapper>

 package com.bjsxt.pojo;

 import java.io.Serializable;

 public class User implements Serializable {
 private int id;
 private String username;
 private String password;
 public String toString() {
     return "User [id=" + id + ", username=" + username + ", password="
             + password + "]";
 }
 public int hashCode() {
     final int prime = 31;
     int result = 1;
     result = prime * result + id;
     result = prime * result + ((password == null) ? 0 : password.hashCode());
     result = prime * result + ((username == null) ? 0 : username.hashCode());
     return result;
 }
 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 (id != other.id)
         return false;
     if (password == null) {
         if (other.password != null)
             return false;
     } else if (!password.equals(other.password))
         return false;
     if (username == null) {
         if (other.username != null)
             return false;
     } else if (!username.equals(other.username))
         return false;
     return true;
 }
 public int getId() {
     return id;
 }
 public void setId(int id) {
     this.id = id;
 }
 public String getUsername() {
     return username;
 }
 public void setUsername(String username) {
     this.username = username;
 }
 public String getPassword() {
     return password;
 }
 public void setPassword(String password) {
     this.password = password;
 }
 public User(int id, String username, String password) {
     super();
     this.id = id;
     this.username = username;
     this.password = password;
 }
 public User() {
     super();
 }

 }

 # Set root category priority to INFO and its only appender to CONSOLE.
 log4j.rootCategory=DEBUG, CONSOLE
 #log4j.rootCategory=INFO, CONSOLE, LOGFILE

 # 单独设置sql语句的输出级别为debug
 #方法级别
 #log4j.logger.com.bjsxt.mapper.UserMapper.selAll=DEBUG
 #类级别
 #log4j.logger.com.bjsxt.mapper.UserMapper=DEBUG
 #包级别
 log4j.logger.com.bjsxt.mapper=DEBUG

 # LOGFILE is set to be a File appender using a PatternLayout.
 log4j.appender.LOGFILE=org.apache.log4j.FileAppender
 #存的位置
 log4j.appender.LOGFILE.File=axis.log
 log4j.appender.LOGFILE.Append=true
 log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
 log4j.appender.LOGFILE.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n