MyBatis初探

首先下载MyBatis jar包， 可以去MyBatis中文官网下载

项目中导入MyBatis jar包和JDBC jar包（此处用的MySQL）

新建conf.xml

内容如下：

<?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"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/yourDatabase"/>
                <property name="username" value="root"/>
                <property name="password" value="yourPassword"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="下面配置文件的路径， 包名全称/???.xml"/>
    </mappers>
</configuration>

　　配置好后写个Student类测试：

 public class Student {
     int id;
     String name;
     int age;
     String sex;

     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;
     }

     public int getAge() {
         return age;
     }

     public void setAge(int age) {
         this.age = age;
     }

     public String getSex() {
         return sex;
     }

     public void setSex(String sex) {
         this.sex = sex;
     }

     @Override
     public String toString() {
         return "Student{" +
                 "id=" + id +
                 ", name='" + name + '\'' +
                 ", age=" + age +
                 ", sex='" + sex + '\'' +
                 '}';
     }
 }

带着toString（）一会print方便

同时在数据库中创建student表，并插入几条数据：

 CREATE TABLE student
 (
     id int PRIMARY KEY,
     name VARCHAR(20),
     age INT,
     sex VARCHAR(4)
 )
 insert into student values(1, '张三', 20, '女');
 insert into student values(2, '李四', 21, '女');
 insert into student values(3, '王五', 22, '男');
 insert into student values(4, '马六', 23, '男');

配置Mapper.xml文件（上方Mapper resource写此文件）

<?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="定位到此的标识符">
    <!-- id为定位到语句的唯一标识符， parameterType为输入参数类型， 只能有一个， 可以用自定义类，returnType-为返回值类型， 也只能有一个， 注意，这两个如果是自定义类需要包名+类名 ->
    <select id="getOneStudent" parameterType="int" resultType="Student">
        select * from student where id=#{id}
    </select>
    <select id="getAllStudents" resultType="Student">
        select * from student
    </select>
</mapper>

用Mapper方式， 定义接口：

 import java.util.List;

 public interface StudentMapper {
     public Student getOneStudent(int id);
     public List<Student> getAllStudents();
 }

下面编写测试类：

 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;
 import java.util.List;

 public class Test {
     public static void main(String[] args) throws IOException {
         String resource = "conf.xml";
         InputStream inputStream = Resources.getResourceAsStream(resource);
         SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
         SqlSession session = sqlSessionFactory.openSession();
         StudentMapper studentMapper = session.getMapper(StudentMapper.class);
         Student s = studentMapper.getOneStudent(1);
         List<Student> arrayStudents = studentMapper.getAllStudents();
         System.out.println(s);
         System.out.println(arrayStudents);
     }

测试成功：