赤裸裸的Mybatis之基础应用小结以及IntelliJ IDEA目录结构的一些小问题

首页 > 代码库 > 赤裸裸的Mybatis之基础应用小结以及IntelliJ IDEA目录结构的一些小问题

赤裸裸的Mybatis之基础应用小结以及IntelliJ IDEA目录结构的一些小问题

2024-10-19 20:56:02 212人阅读

IntelliJ IDEA目录结构的一些小问题

【赤裸裸的Mybatis之基础应用小结】

1、不管怎么样，先建立一个简单的MySQL数据表，如下所示

技术分享

2、接下来要做的事情就是通过Mybatis对数据表进行基础的增删查改，写好bean以及打算实现的方法

import java.util.List;public class PersonDAO {    public void savePerson(Person person) {    }    public void removePersonByName(String name) {    }    public void removePersonByAge(int age) {    }    public List<Person> listPersonByName() {        return null;    }    public List<Person> listPersonByAge() {        return null;    }    public void updatePersonByName() {            }}

3、在写代码之前，先添加必要的依赖包，

        <dependency>            <groupId>mysql</groupId>            <artifactId>mysql-connector-java</artifactId>            <version>5.0.4</version>        </dependency>        <dependency>            <groupId>org.mybatis</groupId>            <artifactId>mybatis</artifactId>            <version>3.4.1</version>        </dependency>        <dependency>            <groupId>log4j</groupId>            <artifactId>log4j</artifactId>            <version>1.2.17</version>        </dependency>

4、要实现上述罗列的方法的第一步就是获取数据表所在数据库的连接，

把配置文件COPY进来，编辑好连接所需要的信息，（mappers先注释掉，顺手把log4j的配置文件也丢进来

在这之前先把项目分好层次，

技术分享

Configuration.xml

<?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="development">    <environment id="development">      <transactionManager type="JDBC">        <property name="" value=""/>      </transactionManager>      <dataSource type="UNPOOLED">        <property name="driver" value="org.gjt.mm.mysql.Driver"/>        <property name="url" value="jdbc:mysql://localhost:3306/my_test"/>        <property name="username" value="root"/>        <property name="password" value="19971019"/>      </dataSource>    </environment>  </environments>   <!--<mappers>-->    <!--<mapper resource="????"/>-->  <!--</mappers>-->  </configuration>

log4j.properties

log4j.rootLogger=DEBUG, MyConsole log4j.appender.MyConsole=org.apache.log4j.ConsoleAppenderlog4j.appender.MyConsole.layout=org.apache.log4j.PatternLayoutlog4j.appender.MyConsole.layout.ConversionPattern=%d [%t] %-5p [%c] - %m%nlog4j.logger.org.apache=INFO

5、我们的最终目的是得到SqlSession类对象，以便通过该对象执行SQL语句，在此之前需要建立SqlSessionFactory，

我将这段代码独立地放在db层下，如下所示：

package db;import java.io.IOException;import java.io.Reader;import org.apache.ibatis.io.Resources;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;/** * 访问数据库类 */public class DBAccess {    public SqlSession getSqlSession() throws IOException {        Reader reader = Resources.getResourceAsReader("Configuration.xml");        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);        SqlSession sqlSession = sqlSessionFactory.openSession();        return sqlSession;    }}

这样就可以方便地获得SqlSession类对象了。

6、真正开始实现personDAO，先把模板COPY到类底下

    private static DBAccess dbAccess = null;    private static SqlSession sqlSession = null;    static {        dbAccess = new DBAccess();        try {            sqlSession = dbAccess.getSqlSession();        } catch (IOException e) {            e.printStackTrace();        }    }    @Override    protected void finalize() throws Throwable {        sqlSession.close();        super.finalize();    }

创建 person.xml 并把模板COPY进来略做修改

<?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="Person">    <resultMap type="bean.Person" id="PersonResult">        <result column="NAME" jdbcType="VARCHAR" property="name"/>        <result column="AGE" jdbcType="INTEGER" property="age"/>    </resultMap></mapper>

修改Configuration.xml 中的 mapper

  <mappers>    <mapper resource="sqlxml/Person.xml"/>  </mappers>

接下来的节奏就是 person.xml --> PersonDAO.java --> 测试 --> person.xml --> PersonDAO.java --> 测试 --> person.xml --> PersonDAO.java --> 测试 --> person.xml --> PersonDAO.java --> 测试 --> person.xml --> PersonDAO.java --> 测试 --> person.xml --> PersonDAO.java --> 测试 --> .... 一个一个方法写下来。在SQL语句中如何获取特定类型的参数值可以参考通过自动回复机器人学Mybatis：OGNL+log4j.properties 里面的图片。

7、完成之后是这个样子的，

person.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="Person">    <resultMap type="bean.Person" id="PersonResult">        <result column="NAME" jdbcType="VARCHAR" property="name"/>        <result column="AGE" jdbcType="INTEGER" property="age"/>    </resultMap>    <insert id="savePerson" parameterType="bean.Person">         INSERT INTO person VALUES (#{name}, #{age})    </insert>    <delete id="removePersonByName" parameterType="String">        DELETE FROM person WHERE name=‘${_parameter}‘    </delete>    <delete id="removePersonByAge" parameterType="int">        DELETE FROM person WHERE name=${_parameter}    </delete>    <select id="listPersonByName" parameterType="String" resultMap="PersonResult">        SELECT name, age FROM person WHERE name=‘${_parameter}‘    </select>    <select id="listPersonByAge" parameterType="int" resultMap="PersonResult">        SELECT name, age FROM person WHERE age=${_parameter}    </select>    <update id="updatePersonByName" parameterType="bean.Person">        UPDATE person SET age=${age} WHERE name=‘${name}‘    </update>    </mapper>

personDAO.java

package dao;import bean.Person;import db.DBAccess;import org.apache.ibatis.session.SqlSession;import java.io.IOException;import java.util.List;public class PersonDAO {    private static DBAccess dbAccess = null;    private static SqlSession sqlSession = null;    static {        dbAccess = new DBAccess();        try {            sqlSession = dbAccess.getSqlSession();        } catch (IOException e) {            e.printStackTrace();        }    }    @Override    protected void finalize() throws Throwable {        sqlSession.close();        super.finalize();    }    public static void main(String[] args) {        Person person = new Person();        person.setName("小王");        person.setAge(23);        PersonDAO personDAO = new PersonDAO();        personDAO.savePerson(person);        // personDAO.removePersonByName("小王");        // personDAO.removePersonByAge(23);        System.out.println(personDAO.listPersonByName("小王"));        for (Person p : personDAO.listPersonByAge(19)) {            System.out.println(p);        }        personDAO.updatePersonByName("小王", 0);    }    public void savePerson(Person person) {        sqlSession.insert("Person.savePerson", person);        sqlSession.commit();    }    public void removePersonByName(String name) {        sqlSession.delete("Person.removePersonByName", name);        sqlSession.commit();    }    public void removePersonByAge(int age) {        sqlSession.delete("Person.removePersonByAge", age);        sqlSession.commit();    }    public List<Person> listPersonByName(String name) {        return sqlSession.selectList("Person.listPersonByName", name);    }    public List<Person> listPersonByAge(int age) {        return sqlSession.selectList("Person.listPersonByAge", age);    }    public void updatePersonByName(String name, int age) {        Person person = new Person();        person.setName(name);        person.setAge(age);        sqlSession.update("Person.updatePersonByName", person);        sqlSession.commit();    }}