MyBatis连接数据库

以下所有步骤流程以及知识点是本人对此次学习的一次总结

首先了解下什么是Mabatis?

mybatis提供一种“半自动化”的ORM实现(ORM（Object/Relational Mapping）即对象/关系数据映射，可以理解为一种数据持久化技术)mybatis着力于POJO与SQL之间的映射关系,可以进行更为细致的SQL优化，可以减少查询字段。

mybatis框架执行流程图

使用MyBatis+maven连接数据库

上面的流程图已经对Mabatis的使用过程进行了大概的叙述,下面就由我亲自实践下!(IDEA)

创建Maven项目

简单介绍下Maven:Maven简化和标准化项目建设过程。处理编译，分配，文档，团队协作和其他任务的无缝连接。 Maven增加可重用性并负责建立相关的任务。

添加jar包

编写Maven中的pom.xml文件,添加需要使用的jar包,以下将要用到4个jar包,分别是:log4j.jar 打印日志文件,方便程序员日后调试;mybatis.jar获得mybatis库;junit.jar:测试项目;mysql-connector-java连接数据库。以下是pom.xml配置信息

http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>cn.bdqn</groupId>
    <artifactId>TestDemo1</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <!--为了获取mybatis库-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.0</version>
        </dependency>
        <!--打印日志文件,方便程序员日后调试-->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>
        <!--mysql连接数据库-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.28</version>
        </dependency>
        <!--junit为了测试-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>RELEASE</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <!-- build这个标签里的内容是为了读取到src/main/java这个目录下的xml文件-->
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
            </resource>
        </resources>
    </build>
    
</project>

创建数据库和表

CREATE TABLE `t_user` ( `id` int(11) NOT NULL AUTO_INCREMENT, `user_name` varchar(20) COLLATE utf8_bin DEFAULT NULL COMMENT '用户名', `password` varchar(20) COLLATE utf8_bin DEFAULT NULL COMMENT '密码', `nick_name` varchar(20) COLLATE utf8_bin DEFAULT NULL COMMENT '昵称', PRIMARY KEY (`id`)) ENGINE=InnoDB AUTO_INCREMENT=15 DEFAULT CHARSET=utf8 COLLATE=utf8_bin;

编写database.properities文件

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/tcmp
jdbc.userName=root
jdbc.passWorld=123

配置mybatis-config.xml文件信息

<?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>
    <!--引入database.properties文件中的信息-->
    <properties resource="database.properties"></properties>
    <!--配置log4j-->
    <settings>
      <setting name="logImpl" value="LOG4J"></setting>
    </settings>
    <!--typeAliases标签中package name可以直接查找到目录下的文件-->
    <typeAliases>
        <package name="cn.bdqn.entity"></package>
    </typeAliases>
    <!--环境配置-->
    <environments default="dev">
        <environment id="dev">
            <!--事务管理-->
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"></property>
                <property name="url" value="${jdbc.url}"></property>
                <property name="username" value="${jdbc.userName}"></property>
                <property name="password" value="${jdbc.passWorld}"></property>
            </dataSource>
        </environment>
    </environments>
    <!-- 通过resource加载单个的映射文件 -->
    <mappers>
        <mapper resource="cn/bdqn/dao/TuserMapper.xml"></mapper>
    </mappers>
</configuration>

编写log4j文件

log4j.rootLogger=DEBUG,CONSOLE,file
log4j.logger.cn.smbms.dao=debug
log4j.logger.com.ibatis=debug 
log4j.logger.com.ibatis.common.jdbc.SimpleDataSource=debug 
log4j.logger.com.ibatis.common.jdbc.ScriptRunner=debug 
log4j.logger.com.ibatis.sqlmap.engine.impl.SqlMapClientDelegate=debug 
log4j.logger.java.sql.Connection=debug 
log4j.logger.java.sql.Statement=debug 
log4j.logger.java.sql.PreparedStatement=debug 
log4j.logger.java.sql.ResultSet=debug 
log4j.logger.org.tuckey.web.filters.urlrewrite.UrlRewriteFilter=debug
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.Threshold=error
log4j.appender.CONSOLE.Target=System.out
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern= [%p] %d %c - %m%n
log4j.appender.file=org.apache.log4j.DailyRollingFileAppender
log4j.appender.file.DatePattern=yyyy-MM-dd
log4j.appender.file.File=log.log
log4j.appender.file.Append=true
log4j.appender.file.Threshold=error
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{yyyy-M-d HH:mm:ss}%x[%5p](%F:%L) %m%n
log4j.logger.com.opensymphony.xwork2=error

                           创建实体类Tuser,并封装数据

public class Tuser {
    private Integer id;
    private String userName,password,nickName;
    public Integer getId() {
        return id;
    }
    public void setId(Integer 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 String getNickName() {
        return nickName;
    }

    public void setNickName(String nickName) {
        this.nickName = nickName;
    }
    public String toString() {
        return "Tuser{" +
                "id=" + id +
                ", userName='" + userName + '\'' +
                ", password='" + password + '\'' +
                ", nickName='" + nickName + '\'' +
                '}';
    }

    
}

                         配置映射文件TuserMapper.xml

<?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命名空间-->
<mapper namespace="cn.bdqn.dao.TuserMapper">
    <!--使用resultType进行输出映射时，只有查询输出结果列名和pojo中的属性名一致才可以，映射成功 -->
    <resultMap id="userMap" type="Tuser">
        <id property="id" column="id"></id>
        <result property="userName" column="user_name"></result>
        <result property="password" column="password"></result>
        <result property="nickName" column="nick_name"></result>
    </resultMap>
    <!--select id取名和接口中的方法名相同-->
    <select id="queryCount" resultType="int">
        SELECT COUNT(*) FROM t_user
    </select>
    <select id="queryAll" resultMap="userMap">
        SELECT * FROM t_user
    </select>
        </mapper>

创建接口TuserMapper(注意!接口名必须和映射文件取名相同)

package cn.bdqn.dao;

import cn.bdqn.entity.Tuser;

import java.util.List;

/**
 * @param
 * @author
 * @data
 */
public interface TuserMapper {
    //查询表中数据条数
    Integer queryCount();
    //查询表中全部数据
    List<Tuser> queryAll();

创建公用的MybatisUtil

package cn.util;

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 java.io.IOException;
import java.io.InputStream;

/**
 * @param
 * @author
 * @data
 */
public class MybatisUtil {
    private  static SqlSessionFactory sqlSessionFactory;
    static {
        try {
            //通过Resources获取mybatis的配置信息并读入io流中
            InputStream in=Resources.getResourceAsStream("mybatis-config.xml");
            //通过sqlSessionFactory创建SqlSessionFactoryBuilder()
            //通过build(in)把输入流中的in添加进来
            sqlSessionFactory=new SqlSessionFactoryBuilder().build(in);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static SqlSession createSqlSession(){
        return  sqlSessionFactory.openSession();
    }
    public static void closeSqlSession(SqlSession sqlSession){
        if(sqlSession!=null){
            sqlSession.close();
        }
    }
}

测试

import cn.bdqn.dao.TuserMapper;
import cn.bdqn.entity.Tuser;
import cn.util.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

/**
 * @param
 * @author
 * @data
 */
public class TestUser {
    @Test
    public void queryAll(){
        SqlSession sqlSession=null;
        try {
            sqlSession=MybatisUtil.createSqlSession();
            //List<Tuser> list=sqlSession.selectList("cn.bdqn.dao.TuserMapper.queryAll");
            //通过getMapper完成映射
            List<Tuser> list=sqlSession.getMapper(cn.bdqn.dao.TuserMapper.class).queryAll();
            if(list!=null){
                for (Tuser tuser : list) {
                    System.out.println(tuser);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally {

           MybatisUtil.closeSqlSession(sqlSession);
        }
    }
    @Test
    public void queryCount(){
        SqlSession sqlSession=null;
        try {
            sqlSession=MybatisUtil.createSqlSession();
            //int n=sqlSession.selectOne("cn.bdqn.dao.TuserMapper.queryCount");
            int n=sqlSession.getMapper(cn.bdqn.dao.TuserMapper.class).queryCount();
            System.out.println(n);
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            MybatisUtil.closeSqlSession(sqlSession);
        }
    }
}