Mybatis应用入门

mybatis简介

Mybatis是在jdbc的基础之上封装而成的持久层框架。
Mybatis是一个ORM框架。ORM（object relational mapping）：对象关系型映射

搭建mybatis环境

 <!-- 设置项目属性 -->
     <properties>
         <argLine>-Dfile.encoding=UTF-8</argLine>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     </properties>
     <!-- 依赖管理 -->
     <dependencies>
         <!-- mysql驱动 -->
         <dependency>
             <groupId>mysql</groupId>
             <artifactId>mysql-connector-java</artifactId>
             <version>5.1.6</version>
         </dependency>
         <!-- mybatis框架 -->
         <dependency>
             <groupId>org.mybatis</groupId>
             <artifactId>mybatis</artifactId>
             <version>3.4.5</version>
         </dependency>
     </dependencies>

mybatis配置文件(配置连接数据库信息)

 在src/main/resources下创建mybatisConfig.xml文件。

 <?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>
     <environments default="mysqlDB">
         <!-- 配置一个数据库连接环境 -->
         <environment id="mysqlDB">
             <transactionManager type="JDBC"></transactionManager>
             <dataSource type="POOLED">
                 <!-- url -->
                 <property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis"></property>
                 <!-- name -->
                 <property name="username" value="root"></property>
                 <!-- password -->
                 <property name="password" value="root"></property>
                 <!-- driver class -->
                 <property name="driver" value="com.mysql.jdbc.Driver"></property>
             </dataSource>
         </environment>
     </environments>
     <!-- mybatis映射文件 -->
     <mappers>
         <mapper resource="mapper/UserEntityMapper.xml"></mapper>
     </mappers>
 </configuration>

主题结构:
<!ELEMENT configuration (properties?, settings?, typeAliases?, typeHandlers?, objectFactory?, objectWrapperFactory?, reflectorFactory?, plugins?, environments?, databaseIdProvider?, mappers?)>
<!ELEMENT mapper (cache-ref | cache | resultMap* | parameterMap* | sql* | insert* | update* | delete* | select* )+>

mybatis映射文件

 <?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.offcn.mybatis.entity">
     <!-- insert -->
     <insert id="insertUser">
         insert into tbl_user values(2,'scott','tiger',25)
     </insert>
 </mapper>

常用API

public class TestMybatis {
    public static void main(String[] args) throws IOException {
        // 加载配置文件
        Reader reader = Resources.getResourceAsReader("mybatisConfig.xml");
        // 创建构造器对象
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        // 创建工厂
        SqlSessionFactory sqlSessionFactory = builder.build(reader);
        //创建执行对象
        SqlSession session = sqlSessionFactory.openSession();
        // 执行sql语句
        session.insert("insertUser");
        // 提交事务
        session.commit();
        session.close();
    }
}

向SQL语句传参数方式

 （1）传对象

     <update id="updateUser" parameterType="UserEntity">
         update tbl_user set
         uname=#{uname},upass=#{upass},uage=#{uage} where
         uid=#{uid}
     </update>
      public void updateUser() {
         UserEntity user = new UserEntity(8, "紫衫龙王", "qkdny", 41);
         // 创建执行对象
         SqlSession session = sqlSessionFactory.openSession();
         // 执行sql语句
         session.insert("updateUser", user);
         // 提交事务
         session.commit();
         session.close();
     }
 （2）传map对象
          public void queryMap() {
         // 构造条件
         Map<String, Object> map = new HashMap<String, Object>();
         map.put("name", "scott");
         map.put("password", "tiger");
         // 创建执行对象
         SqlSession session = sqlSessionFactory.openSession();
         // 执行sql语句
         List<UserEntity> list = session.selectList("queryMap", map);
         for (UserEntity user : list) {
             System.out.println(user);
         }
         session.close();
     }
     <!-- 根据用户名和密码查询 -->
         <select id="queryMap" resultType="UserEntity" parameterType="java.util.Map">
         SELECT uid,uname,upass,uage from tbl_user where uname=#{name} and upass=#{password}
     </select>
 （3）直接传变量
      public void queryById() {
         // 创建执行对象
         SqlSession session = sqlSessionFactory.openSession();
         // 执行sql语句
         UserEntity user = (UserEntity) session.selectOne("queryById", 5);
         System.out.println(user);
         session.close();
     }
     <select id="queryById" parameterType="int" resultType="UserEntity">
         SELECT uid,uname,upass,uage from tbl_user where uid=#{uid}
     </select>

使用实体类别名

 <typeAliases>
     <!-- 设置实体类别名 -->  要根据属性顺序设置该属性,不然配置文件报错
     <typeAlias type="com.offcn.mybatis.entity.UserEntity" alias="UserEntity"></typeAlias>
 </typeAliases>

     <insert id="insertUserWithParam" parameterType="UserEntity">//此处就可以使用别名了
         insert into tbl_user(uid,uname,upass,uage) values(#{uid},#{uname},#{upass},#{uage})
     </insert>

获取sql结果的方式

获取对象
<!-- query id resultType:设定返回值-->
    <select id="queryById" parameterType="int" resultType="UserEntity">
     SELECT uid,uname,upass,uage from tbl_user where uid=#{uid}
    </select>

    @Test
    public void queryById() {
        // 创建执行对象
        SqlSession session = sqlSessionFactory.openSession();
        // 执行sql语句,获取对象
        UserEntity user =(UserEntity)session.selectOne("queryById", 5);
        System.out.println(user);
        session.close();
    }

获取集合
<!-- query All -->
    <select id="queryAll" resultType="UserEntity">
        SELECT uid,uname,upass,uage from tbl_user
    </select>
    @Test
    public void queryAll() {
        // 创建执行对象
        SqlSession session = sqlSessionFactory.openSession();
        // 执行sql语句,获取list集合
        List<UserEntity> list=session.selectList("queryAll");
        for(UserEntity user:list) {
            System.out.println(user);
        }
        session.close();
    }

简单日志使用

 导入log4j依赖

     <dependency>
             <groupId>log4j</groupId>
             <artifactId>log4j</artifactId>
             <version>1.2.15</version>
     </dependency>

 resources下创建日志文件log4j.properties

 ### set log levels ###
 log4j.rootLogger = debug,stdout,log
 #, log, index, D, I, W, E

 ###  print log to console ###
 log4j.appender.stdout = org.apache.log4j.ConsoleAppender
 log4j.appender.stdout.Target = System.out
 log4j.appender.stdout.layout = org.apache.log4j.PatternLayout
 log4j.appender.stdout.layout.ConversionPattern = %d %p [%c] - <%m>%n

 ### create log to file ###
 log4j.appender.log = org.apache.log4j.DailyRollingFileAppender
 log4j.appender.log.File = /logs/log.log
 log4j.appender.log.Append = true
 log4j.appender.log.layout = org.apache.log4j.PatternLayout
 log4j.appender.log.layout.ConversionPattern= %d %p [%c] - <%m>%n

 # Control logging for other open source packages
 log4j.logger.net.sf.navigator=ERROR
 log4j.logger.net.sf.acegisecurity=WARN
 log4j.logger.net.sf.acegisecurity.intercept.event.LoggerListener=WARN
 log4j.logger.org.apache.commons=ERROR
 log4j.logger.org.apache.struts=WARN
 log4j.logger.org.displaytag=ERROR
 log4j.logger.org.springframework=WARN
 log4j.logger.org.apache.velocity=WARN

 # SqlMap logging configuration...
 log4j.logger.com.ibatis=debug
 log4j.logger.com.ibatis.db=debug
 log4j.logger.com.ibatis.common.jdbc.SimpleDataSource=debug
 log4j.logger.com.ibatis.sqlmap.engine.cache.CacheModel=debug
 log4j.logger.com.ibatis.sqlmap.engine.impl.SqlMapClientImpl=debug
 log4j.logger.com.ibatis.sqlmap.engine.builder.xml.SqlMapParser=debug
 log4j.logger.com.ibatis.common.util.StopWatch=debug

 log4j.logger.java.sql.Connection=debug
 log4j.logger.java.sql.Statement=error
 log4j.logger.java.sql.PreparedStatement=debug
 log4j.logger.java.sql.ResultSet=error

 日志级别
 A：off 最高等级，用于关闭所有日志记录。
 B：fatal 指出每个严重的错误事件将会导致应用程序的退出。
 C：error 指出虽然发生错误事件，但仍然不影响系统的继续运行。
 D：warn 表明会出现潜在的错误情形。
 E：info 一般和在粗粒度级别上，强调应用程序的运行全程。
 F：debug 一般用于细粒度级别上，对调试应用程序非常有帮助。
 G：all 最低等级，用于打开所有日志记录。