Java_myBatis_入门写法

Posted 2021-01-03 张啊咩

一.整体步骤

1.读取全局配置文件“SqlMapConfig.xml”

2.用SqlSessionFactoryBuilder来创建一个SqlSessionFactory

3.用创建好的SqlSessionFactory创建一个SqlSession

4.用创建好的SqlSession来读取对应的映射配置文件“Mapper1.xml”，并传入参数

5.返回结果

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二.具体步骤

1.新建maven项目

eclipse菜单找到“File”->"new"->"Project",选择Maven Project

2.在配置文件pom.xml下的denpencies添加denpency

mybatis的jar包和mysql的jdbc驱动

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.4.6</version>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.35</version>
</dependency>

3.在src/main下新建资源文件夹"resources",并添加SqlMapConfig.xml、具体映射配置文件Mapper.xml和数据库参数文件db.properties

SqlMapConfig.xml源码:

<?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"></properties>
  <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC"/>
      <dataSource type="POOLED">
        <property name="driver" value="${driver}"/>
        <property name="url" value="${url}"/>
        <property name="username" value="${username}"/>
        <property name="password" value="${password}"/>
      </dataSource>
    </environment>
  </environments>
  <mappers>
    <mapper resource="StudentMapper.xml"/>
  </mappers>
</configuration>

 db.properties的源码：

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8
username=root
password=123456

Mapper.xml的源码

<?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="test">
    <select id="selectPerson" parameterType="int" resultType="com.mavenTest.mybatis_test.Person">
        select * from Persons_table where id = #{id}
    </select>
</mapper>

#{}：是经过处理的相当于JDBC的PreparedStatement，简单类型时“{}”里可以写任意名字（甚至是中文）

${}：是原样输出相当于JDBC的Statement，简单类型时“{}”里必须写“value”

4.在main/java下的任意jar包中创建一个pojo，这里例如是Person.class（注意对应好上面的resultType的路径）

public class Person{
    private int id;
    private String name;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

5.在java/main的任意jar包创建一个任意类

 

public class pratise {
    public static void main(String[] args) throws IOException{
        // 读取全局配置文件
        InputStream is = Resources.getResourceAsStream("SqlMapConfig.xml");
        // 用SqlSessionFactoryBuilder来创建SqlSessionFactory实例
        SqlSessionFactory ssf = new SqlSessionFactoryBuilder().build(is);
        // 用SqlSessionFactory实例来创建SqlSession实例
        SqlSession ss = ssf.openSession();
        // 通过SqlSession实例来查询映射配置文件，然后传入参数，执行sql语句
        Student s = ss.selectOne("selectStudent", 827);
        // 关闭SqlSession实例
        ss.close();
        System.out.println(s.getName());
    }
}

 

 

 

 这样就已经可以实现数据库语句的调用了