mybatis 入门搭建

清疚 2022-10-01 10:55 92阅读 0赞

# 首先导包 #

依赖如下

<dependencies>
        <dependency>
          <groupId>mysql</groupId>
          <artifactId>mysql-connector-java</artifactId>
          <version>8.0.15</version>
        </dependency>
        <dependency>
          <groupId>org.mybatis</groupId>
          <artifactId>mybatis</artifactId>
          <version>3.5.1</version>
        </dependency>
        <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>4.11</version>
          <scope>test</scope>
        </dependency>
      </dependencies>
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# 构建SqlSessionFactory #

MyBatis应用是以SqlSessionFactory为中心的,实例可以通过SqlSessionFactoryBuilder获得. 其中SqlSessionFactory是工厂接口,任务用于创建SqlSession 配置文件将会解析配置XML文件在Configuration类对象中.

## 配置XML获取数据源,事务管理器,映射器 ##

在resource文件下新建mybatis-config.xml文件 配置文件内容如下

<?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>
    	
    	<typeAliases>
    		<typeAlias type="com.ming.Role" alias="role"/>
    	</typeAliases>
    	
    	
    	<environments default="development">
    		<environment id="development">
    			
    			<transactionManager type="JDBC"></transactionManager>
    			
    			<dataSource type="POOLED">
    				<property name="driver" value="com.mysql.cj.jdbc.Driver"/>
    				<property name="url" value="jdbc:mysql://47.94.95.84:32786/mybatis"/>
    				<property name="username" value="mybatis"/>
    				<property name="password" value="ABCcba20170607"/>
    			</dataSource>
    		</environment>
    	</environments>
    </configuration>
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新建类

package com.ming;
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    import java.io.IOException;
    import java.io.InputStream;
    
    public class Role {
        public String getSqlSessionFactory(){
            String resource = "mybatis-config.xml";
            try {// 获得输入流
                InputStream inputStream;
                inputStream = Resources.getResourceAsStream(resource);
                // 获得SqlSessionFactory工厂
                SqlSessionFactory sqlSessionFactory = null;
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            }catch (IOException e){
                e.printStackTrace();
            }
            return null;
        }
    }
    
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最后新建测试类

package com.ming;
    
    import org.junit.After;
    import org.junit.Before;
    import org.junit.Test;
    
    public class RoleTest {
        private Role role = null;
        @Before
        public void setUp() throws Exception {
            this.role = new Role();
        }
    
        @After
        public void tearDown() throws Exception {
        }
    
        @Test
        public void getSqlSessionFactory() {
            role.getSqlSessionFactory();
        }
    }
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此时的目录结构

## 代码方式构建 ##

public SqlSessionFactory getSqlSessionFactory1(){
            // 创建数据库连接池
            PooledDataSource dataSource = new PooledDataSource();
            dataSource.setDriver("com.mysql.cj.jdbc.Driver");
            dataSource.setUrl("jdbc:mysql://47.94.95.84:32786/mybatis");
            dataSource.setUsername("mybatis");
            dataSource.setPassword("ABCcba20170607");
            // 构建数据库事物
            TransactionFactory transactionFactory = new JdbcTransactionFactory();
            // 创建数据库环境
            Environment environment = new Environment("development", transactionFactory, dataSource);
            // 构建Configuration对象
            Configuration configuration = new Configuration(environment);
            // 注册上下文别名
            configuration.getTypeAliasRegistry().registerAlias("role", Role.class);
            // 创建映射器
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);
            return sqlSessionFactory;
        }
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书写测试用例如下

# 创建SqlSession #

SqlSession属于门面,通过SqlSession可以获得需要的什么信息

SqlSession sqlSession = null;
            try{
                // 创建一个sqlsession会话
                sqlSession = sqlSessionFactory.openSession();
                sqlSession.commit();
            }catch (Exception e){
                // 输出错误信息
                System.out.println(e.getMessage());
                // 进行事物操作,回滚数据库数据
                sqlSession.rollback();
            }finally {
                // 进行资源关闭
                if(sqlSession != null){
                    sqlSession.close();
                }
            }
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SqlSession作用,获取映射器,通过命名信息执行sql结果

# 映射器 #

映射器由java和xml文件共同组成,作用 定义参数类型 描述缓存 描述sql 定义查询结果和POJO映射关系

先给出java接口

package com.ming;
    
    public interface RoleMapper {
        public Role getRole(Long id);
    }
    
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根据给定的id获取角色对象

给出映射文件,然后在生成的时候会根据接口实现类,生成对象.

先编写POJO

package com.ming;
    
    // POJO
    public class Role {
        private int id;
        private String roleName;
        private String note;
    
        public void setId(int id) {
            this.id = id;
        }
    
        public void setRoleName(String roleName) {
            this.roleName = roleName;
        }
    
        public void setNote(String note) {
            this.note = note;
        }
    
        public int getId() {
            return id;
        }
    
        public String getRoleName() {
            return roleName;
        }
    
        public String getNote() {
            return note;
        }
    }
    
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在编写映射配置文件

<?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="com.ming.RoleMapper">
    	
    	<select id="getRole" parameterType="int" resultType="role">
    		
    		SELECT id, role_name as roleName, note FROM t_role WHERE id = #{id}
    	</select>
    </mapper>
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最后编写mybatis,添加映射器配置文件

最后再编写执行sql的类

package com.ming;
    import org.apache.ibatis.datasource.pooled.PooledDataSource;
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.mapping.Environment;
    import org.apache.ibatis.session.Configuration;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    import org.apache.ibatis.transaction.TransactionFactory;
    import org.apache.ibatis.transaction.jdbc.JdbcTransactionFactory;
    
    import java.io.IOException;
    import java.io.InputStream;
    
    public class MyBatis {
        public String getSqlSessionFactory(){
            String resource = "mybatis-config.xml";
            SqlSessionFactory sqlSessionFactory = null;
            try {// 获得输入流
                InputStream inputStream;
                inputStream = Resources.getResourceAsStream(resource);
                // 获得SqlSessionFactory工厂
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            }catch (IOException e){
                e.printStackTrace();
            }
            SqlSession sqlSession = null;
            try{
                // 创建一个sqlsession会话
                sqlSession = sqlSessionFactory.openSession();
                // 获得映射器
                // 接口传入映射器中
                RoleMapper roleMapper = sqlSession.getMapper(RoleMapper.class);
                // 执行方法
                Role role = roleMapper.getRole(0);
                System.out.println(role.getRoleName());
                // 刷新语句并提交链接
                sqlSession.commit();
            }catch (Exception e){
                // 输出错误信息
                System.out.println(e.getMessage());
                // 进行事物操作,回滚数据库数据
                sqlSession.rollback();
            }finally {
                // 进行资源关闭
                if(sqlSession != null){
                    sqlSession.close();
                }
            }
            return null;
        }
    
        public SqlSessionFactory getSqlSessionFactory1(){
            // 创建数据库连接池
            PooledDataSource dataSource = new PooledDataSource();
            dataSource.setDriver("com.mysql.cj.jdbc.Driver");
            dataSource.setUrl("jdbc:mysql://47.94.95.84:32786/mybatis");
            dataSource.setUsername("mybatis");
            dataSource.setPassword("ABCcba20170607");
            // 构建数据库事物
            TransactionFactory transactionFactory = new JdbcTransactionFactory();
            // 创建数据库环境
            Environment environment = new Environment("development", transactionFactory, dataSource);
            // 构建Configuration对象
            Configuration configuration = new Configuration(environment);
            // 注册上下文别名
            configuration.getTypeAliasRegistry().registerAlias("role", MyBatis.class);
            // 创建映射器
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);
            return sqlSessionFactory;
        }
    }
    
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最后编写测试类

package com.ming;
    
    import org.junit.After;
    import org.junit.Before;
    import org.junit.Test;
    
    public class MyBatisTest {
        private MyBatis myBatis = null;
        @Before
        public void setUp() throws Exception {
            this.myBatis = new MyBatis();
        }
    
        @After
        public void tearDown() throws Exception {
        }
    
        @Test
        public void getSqlSessionFactory() {
            myBatis.getSqlSessionFactory();
        }
    
        @Test
        public void getSqlSessionFactory1() {
            myBatis.getSqlSessionFactory1();
        }
    }
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执行单元测试 结果如下

即完成了MyBatis的一次查询

## 注解 ##

定义接口

package com.ming;
    
    import org.apache.ibatis.annotations.Select;
    
    public interface Role1 {
        @Select (value="SELECT id, role_name as roleName, note FROM t_role WHERE id = #{id}")
        public Role getRole(int id);
    }
    
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# 生命周期 #

## SqlSessionFactoryBuilder ##

其是利用xml或者java编码构建SqlSessionFactory 可以构建多个SessionFactory 作用 构建器 根据构建器获得sqlSessionFactory

## SqlSessionFactory ##

创建SqlSession 一个SqlSession相当于JDBC的Connection对象 此为单例管理 每创建一个SqlSession就会创建一个数据库连接

## SqlSession ##

此为一个会话,相当于一个Connection连接 线程不安全 生命周期为一个应用的请求和操作,可以执行多条sql

转载于:https://juejin.im/post/5cab75f8e51d456e2a64b272