mybatis详解-(10)别名

淡淡的烟草味﹌ 2022-06-03 00:07 197阅读 0赞

前面已经介绍到了参数的传递，但是在真个过程中都使用的是全类名。本篇介绍使用别名：

# 1.创建实体类 #

package org.mybatis.typeAliases;
    
    import org.apache.ibatis.type.Alias;
    
    public class Employee { 
        private Integer id;
        private String lastName;
        private String email;
        private String gender;
    
        public Integer getId() {
            return id;
        }
        public void setId(Integer id) {
            this.id = id;
        }
        public String getLastName() {
            return lastName;
        }
        public void setLastName(String lastName) {
            this.lastName = lastName;
        }
        public String getEmail() {
            return email;
        }
        public void setEmail(String email) {
            this.email = email;
        }
        public String getGender() {
            return gender;
        }
        public void setGender(String gender) {
            this.gender = gender;
        }
        @Override
        public String toString() {
            return "Employee [id=" + id + ", lastName=" + lastName + ", email=" + email
                    + ", gender=" + gender + "]";
        }
    }

# 2.创建mapper接口 #

package org.mybatis.typeAliases;
    
    public interface EmployeeMapper { 
    
        public Employee getEmpById(Integer id);
    
    }

# 3.创建主配置文件 #

<?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>
    
        
        <settings>
            <setting name="mapUnderscoreToCamelCase" value="true"/>
        </settings>
    
        
        <typeAliases>
            
            <typeAlias type="org.mybatis.typeAliases.Employee" alias="emp"/>
        </typeAliases>
    
    
        
        <environments default="dev_mysql">
            <environment id="dev_mysql">
                <transactionManager type="JDBC" />
                <dataSource type="POOLED">
                    <property name="driver" value="${mysql.driver}" />
                    <property name="url" value="${mysql.url}" />
                    <property name="username" value="${mysql.username}" />
                    <property name="password" value="${mysql.password}" />
                </dataSource>
            </environment>
    
        </environments> 
        <mappers>
            <mapper resource="mapper/typeAliasesmapper.xml"/>
        </mappers>
    
    </configuration>

# 4.创建mapper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="org.mybatis.typeAliases.EmployeeMapper">
        
        <select id="getEmpById" resultType="emp">
            select id,last_name,email,gender from mybatis_employee where id = #{id}
        </select>
    </mapper>

# 5.创建测试类 #

package org.mybatis.typeAliases;
    
    import java.io.IOException;
    import java.io.InputStream;
    
    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 org.junit.Test;
    import org.mybatis.typeAliases.Employee;
    
    /** * 使用接口式編程 */
    public class MybatisTest { 
    
        @Test
        public void testMybatis() {
            String resource = "mybatis-config-typeAliases.xml";//全局配置文件
    
            InputStream inputStream = null;
            SqlSessionFactory sqlSessionFactory = null;
            SqlSession sqlSession = null;
            try {
                inputStream = Resources.getResourceAsStream(resource);
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
                sqlSession = sqlSessionFactory.openSession();
    
                EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);
                Employee emp = mapper.getEmpById(2);
                System.out.println(emp);
    
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                sqlSession.close();
            }
        }
    }

# 6.测试结果 #

> DEBUG - Logging initialized using ‘class org.apache.ibatis.logging.slf4j.Slf4jImpl’ adapter.  
> DEBUG - PooledDataSource forcefully closed/removed all connections.  
> DEBUG - PooledDataSource forcefully closed/removed all connections.  
> DEBUG - PooledDataSource forcefully closed/removed all connections.  
> DEBUG - PooledDataSource forcefully closed/removed all connections.  
> DEBUG - Openning JDBC Connection  
> DEBUG - Created connection 665188480.  
> DEBUG - ooo Using Connection \[com.mysql.jdbc.JDBC4Connection@27a5f880\]  
> DEBUG - ==> Preparing: select id,last\_name,email,gender from mybatis\_employee where id = ?  
> DEBUG - ==> Parameters: 2(Integer)  
> Employee \[id=2, lastName=lisi, email=tang\_greatman@qq.com, gender=2\]  
> DEBUG - Resetting autocommit to true on JDBC Connection \[com.mysql.jdbc.JDBC4Connection@27a5f880\]  
> DEBUG - Closing JDBC Connection \[com.mysql.jdbc.JDBC4Connection@27a5f880\]  
> DEBUG - Returned connection 665188480 to pool.

# 7.使用注解方案 #

Employee实体添加注解empp

@Alias("empp")
    public class Employee { 
        private Integer id;
        private String lastName;
        private String email;
        private String gender;

主配置文件使用包扫描

映射配置文件使用别名empp

<select id="getEmpById" resultType="empp">
    select id,last_name,email,gender from mybatis_employee where id = #{id}
    </select>

运行结果：

> DEBUG - Checking to see if class org.mybatis.typeAliases.MybatisTest matches criteria \[is assignable to Object\]  
> DEBUG - PooledDataSource forcefully closed/removed all connections.  
> DEBUG - PooledDataSource forcefully closed/removed all connections.  
> DEBUG - PooledDataSource forcefully closed/removed all connections.  
> DEBUG - PooledDataSource forcefully closed/removed all connections.  
> DEBUG - Openning JDBC Connection  
> DEBUG - Created connection 1399499405.  
> DEBUG - ooo Using Connection \[com.mysql.jdbc.JDBC4Connection@536aaa8d\]  
> DEBUG - ==> Preparing: select id,last\_name,email,gender from mybatis\_employee where id = ?  
> DEBUG - ==> Parameters: 2(Integer)  
> Employee \[id=2, lastName=lisi, email=tang\_greatman@qq.com, gender=2\]  
> DEBUG - Resetting autocommit to true on JDBC Connection \[com.mysql.jdbc.JDBC4Connection@536aaa8d\]  
> DEBUG - Closing JDBC Connection \[com.mysql.jdbc.JDBC4Connection@536aaa8d\]  
> DEBUG - Returned connection 1399499405 to pool.