mybatis详解-(13)注解操作查询

港控/mmm° 2022-06-03 03:12 261阅读 0赞

前面讲述的内容中，基本都是按照同样的步骤1）创建接口类，2）创建主配置文件，3）创建接口映射文件。在接口类中定义实现的接口功能，在映射配置文件中写具体的完成接口类容的sql语句，然后在主配置文件中应用映射配置文件操作相关的操作。mybatis也提供了一套通过接口操作数据请求的注解，比如要完成一个查询操作，可以按照如下的步骤完成：

# 1.创建实体类 #

Employee

package org.mybatis.annotation;
    
    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.创建方法接口类 #

EmployeeAnnotation  
在接口方法上面添加@Select注解，在注解中添加实际的操作sql语句。还有其他的相关注解如@Insert等，更详细的内容可参考[MybatisApi][]

package org.mybatis.annotation;
    
    import org.apache.ibatis.annotations.Select;
    
    public interface EmployeeAnnotation { 
    
        @Select("select * from mybatis_employee where id = #{id}")
        public Employee getEmployeeById(int id);
    
    }

# 3.创建主配置文件 #

mybatis-config-annotation.xml  
在主配置文件中引用接口类org.mybatis.annotation.EmployeeAnnotation

<?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>
    
        <environments default="development">
            <environment id="development">
                <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 class="org.mybatis.annotation.EmployeeAnnotation"/>
    
            
            
        </mappers>
    
    </configuration>

# 4.创建测试类 #

package org.mybatis.annotation;
    
    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;
    
    /** * 使用接口式編程 */
    public class MybatisTest { 
    
        @Test
        public void testMybatis() {
            String resource = "mybatis-config-annotation.xml";
    
            InputStream inputStream = null;
            SqlSessionFactory sqlSessionFactory = null;
            SqlSession sqlSession = null;
            try {
                inputStream = Resources.getResourceAsStream(resource);
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
                sqlSession = sqlSessionFactory.openSession();
    
                EmployeeAnnotation mapper = sqlSession.getMapper(EmployeeAnnotation.class);
    
                Employee employee = mapper.getEmployeeById(2);
    
                System.out.println(employee);
    
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                sqlSession.close();
            }
        }
    }

# 5.测试结果 #

> DEBUG - Openning JDBC Connection  
> DEBUG - Created connection 527446182.  
> DEBUG - ooo Using Connection \[com.mysql.jdbc.JDBC4Connection@1f7030a6\]  
> DEBUG - ==> Preparing: select \* 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 \[com.mysql.jdbc.JDBC4Connection@1f7030a6\]  
> DEBUG - Closing JDBC Connection \[com.mysql.jdbc.JDBC4Connection@1f7030a6\]  
> DEBUG - Returned connection 527446182 to pool.

这个步骤中省略了创建映射配置文件的步骤，直接在主配置文件中引用接口类。  
但是这种方式也存在一定的问题，比如这样操作是硬编码，为以后的修改和调试都埋下隐患。建议还是使用映射配置文件的方式来操作。

[MybatisApi]: http://www.mybatis.org/mybatis-3/zh/java-api.html