First create a new JavaWeb project and import the jar package that mybatis depends on. At the same time, Mybatis operates on the database, so we need to create a new table user in the database for demonstration.
After creating the new table, we also need to create the corresponding entity class User.java and add set and get methods:
public class User { private String username; private String password; private int age; 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 int getAge() { return age; } public void setAge(int age) { this.age = age; } }
In Mybatis, we need to create a mapping file userMapper.xml corresponding to the entity class:
<?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"> <!-- 为这个mapper指定一个唯一的namespace,namespace的值习惯上设置成包名+sql映射文件名) --> <mapper namespace="com.mybatis.mapping.userMapper"> <!-- 在select标签中编写查询的SQL语句,id属性值必须是唯一的 使用parameterType属性指明查询时使用的参数类型,resultType属性指明查询返回的结果集类型 --> <!-- 根据username查询得到一个user对象 --> <select id="getUser" parameterType="java.lang.String" resultType="com.mybatis.po.User"> select * from user where username=#{username} </select> <delete id="deleteUser" parameterType="java.lang.String"> delete from user where username=#{username} </delete> </mapper>
Finally, we need to create a new configuration file config.xml for Mybatis and database connection under src, and import the above userMapper.xml. The code is as follows:
<?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" /> <!-- 配置数据库连接信息 --> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver" /> <property name="url" value="jdbc:mysql://localhost:3306/test" /> <property name="username" value="root" /> <property name="password" value="" /> </dataSource> </environment> </environments> <mappers> <!-- 注册userMapper.xml文件,resource为userMapper.xml所在目录--> <mapper resource="com/mybatis/mapping/userMapper.xml"/> </mappers> </configuration>
The configuration database connection information here is not very different from Hibernate. Now we create a new Use a Test class to test it:
public class Test { public static void main(String[] args) throws IOException { //mybatis的配置文件 String resource = "config.xml"; //使用类加载器加载mybatis的配置文件(它也加载关联的映射文件) InputStream is = Test.class.getClassLoader().getResourceAsStream(resource); //构建sqlSession的工厂 SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is); //打开session SqlSession session = sessionFactory.openSession(); /** * 映射sql的标识字符串 *com.mybatis.mapping.userMapper是userMapper.xml文件中mapper标签的namespace属性的值, * getUser是select标签的id属性值,通过select标签的id属性值就可以找到要执行的SQL */ String statement = "com.mybatis.mapping.userMapper.getUser";//映射sql的标识字符串 //执行查询返回一个唯一user对象的sql User user = session.selectOne(statement,"username1"); System.out.println(user.getUsername()); String statement2="com.mybatis.mapping.userMapper.deleteUser"; session.delete(statement2,user); } }
Executing the selectOne method will return a user object (if you want to query multiple pieces of data, you can use selectList. This method will return a List
The above is a simple example of Mybatis. Of course, in userMapper.xml, we can also use OGNL to generate dynamic sql statements. If you are interested, you can study it yourself.