MyBatis入门案列

清疚 2024-03-17 20:32 67阅读 0赞

## MyBatis入门案列 ##

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### 开发Mybatis程序的步骤： ###

1、配置mybatis  
`conf.xml`: 配置数据库信息 和 需要加载的映射文件

２、表 - 类  
映射文件`xxMapper.xml`: 增删改查标签`<select>`

３、测试类:  
`session.selectOne`(“**需要查询的SQL的namespace.id**”, “**SQL的参数值**”);

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**运行环境**：数据库 Oracle19c，Java8，数据库连接驱动 ojdbc8.jar，mybatis-3.4.6.jar 、eclipse

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### 具体实现类： ###

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１、建表：

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CREATE TABLE person(id NUMBER,  name VARCHAR2(20), age NUMBER);
    
    INSERT　into person  VALUES(1,'zs', 23);
    
    commit;

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２、配置mybatis

`conf.xml`:配置数据库信息 和 需要加载的映射文件

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<?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="oracle.jdbc.OracleDriver" />
    				<property name="url" value="jdbc:oracle:thin:@127.0.0.1:1521:ORCL" />
    				<property name="username" value="scott" />
    				<property name="password" value="tiger" />
    			</dataSource>
    		</environment>
    	</environments>
    	<mappers>
    		
    		<mapper resource="org/lanqiao/entity/personMapper.xml" />
    	</mappers>
    </configuration>

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３、`表 - 类`：新建与数据库对应的Bean类，同时构建`映射文件`。

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package org.lanqiao.entity;
    
    public class Person {
        
    	private int id;
    	private String name;
    	private int age;
    
    	public Person() {
        
    	}
    
    	public Person(int id, String name, int age) {
        
    		super();
    		this.id = id;
    		this.name = name;
    		this.age = age;
    	}
    
    	// getter and setter
    	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;
    	}
    
    	@Override
    	public String toString() {
        
    		return "Person [id=" + id + ", name=" + name + ", age=" + age + "]";
    	}
    
    }

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映射文件personMapper.xml:增删改查标签`<select>`

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<?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="org.lanqiao.entity.personMapper">
    
    	<select id="queryPersonById" resultType="org.lanqiao.entity.Person" parameterType="int">
    		select * from person where id = #{id}
    	</select>
    
    </mapper>

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４、编写测试类`TestMybatis.java`：

session.selectOne(“需要查询的SQL的namespace.id”, “SQL的参数值”);

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package org.lanqiao.entity;
    
    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;
    
    public class TestMybatis {
        
    	public static void main(String[] args) throws IOException {
        
    		// 加载myBatis配置文件（为了访问数据库）
    		Reader reader = Resources.getResourceAsReader("conf.xml");
    		SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
    
    		// SqlSessionFactory connection
    		SqlSession session = sessionFactory.openSession();
    		String statement = "org.lanqiao.entity.personMapper.queryPersonById";
    		Person person = session.selectOne(statement,1);
    		System.out.println(person);
    		session.close();
    
    	}
    
    }

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５、执行结果

![在这里插入图片描述][290c9229cf7142c1a52d72657ae7810b.png]

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６、小结

1.  parameterType=“int”> 的 `int` 对应 select 语句的 \#\{ `id`\}

select * from person where id = #{id}

1.  namespace：映射文件的路径

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[290c9229cf7142c1a52d72657ae7810b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/14/74d7040f4f69458896945e820567e999.png