mybatis之注解式开发

注解：

• 注解是用于描述代码的代码。例如：@Test（用于描述方法进行junit测试），@Override(用于描述方法的重写),@Param（用于描述属性的名称）
• 注解的使用风格：@xxx（属性），使用前必须进行导包
• 使用注解一般用于简化配置文件，但是注解有时候也不是很友好(有时候反而更麻烦)，例如动态sql
• 关于注解的属性

属性的设定方式是：属性名=属性值

• 关于属性的类型

1. 基本类型和String，可以直接使用双引号的形式
2. 数组类型，name={值1，值2，......}如果数组元素只有一个，可以省略大括号。
3. 对象类型，name=@对象名（属性）
4. 如果属性是该注解的默认注解，而且该注解只配置这一个属性，key将属性名省略。

mybatis注解之CURD代码如下

 package com.bjsxt.mapper;
 
 import java.util.List;
 
 import org.apache.ibatis.annotations.Delete;
 import org.apache.ibatis.annotations.Insert;
 import org.apache.ibatis.annotations.Select;
 import org.apache.ibatis.annotations.Update;
 
 import com.bjsxt.pojo.Student;
 
 public interface StudentMapper {
 
     @Select("select * from t_student")
     List<Student> selAll();
 
     @Insert("insert into t_student values (default, #{name}, #{age}, #{gender}, #{cid})")
     int insStu(Student student);
 
     @Update("update t_student set age=#{1} where id=#{0}")
     int updStu(int id, int age);
 
     @Delete("delete from t_student where id=#{0}")
     int delStu(int id);
 }

 package com.bjsxt.pojo;
 
 import java.io.Serializable;
 
 public class Student implements Serializable {
 
     private int id;
     private String name;
     private int age;
     private String gender;
     private int cid;
 
     public Student() {
         super();
     }
 
     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;
     }
 
     public String getGender() {
         return gender;
     }
 
     public void setGender(String gender) {
         this.gender = gender;
     }
 
     public int getCid() {
         return cid;
     }
 
     public void setCid(int cid) {
         this.cid = cid;
     }
 
     @Override
     public int hashCode() {
         final int prime = 31;
         int result = 1;
         result = prime * result + age;
         result = prime * result + cid;
         result = prime * result + ((gender == null) ? 0 : gender.hashCode());
         result = prime * result + id;
         result = prime * result + ((name == null) ? 0 : name.hashCode());
         return result;
     }
 
     @Override
     public boolean equals(Object obj) {
         if (this == obj)
             return true;
         if (obj == null)
             return false;
         if (getClass() != obj.getClass())
             return false;
         Student other = (Student) obj;
         if (age != other.age)
             return false;
         if (cid != other.cid)
             return false;
         if (gender == null) {
             if (other.gender != null)
                 return false;
         } else if (!gender.equals(other.gender))
             return false;
         if (id != other.id)
             return false;
         if (name == null) {
             if (other.name != null)
                 return false;
         } else if (!name.equals(other.name))
             return false;
         return true;
     }
 
     @Override
     public String toString() {
         return "Student [id=" + id + ", name=" + name + ", age=" + age + ", gender=" + gender + ", cid=" + cid + "]";
     }
 }

 package com.bjsxt.test;
 
 import java.util.List;
 
 import org.apache.ibatis.session.SqlSession;
 import org.junit.Test;
 
 import com.bjsxt.mapper.StudentMapper;
 import com.bjsxt.pojo.Student;
 import com.bjsxt.util.MyBatisUtil;
 
 public class TestStu {
 
     @Test
     public void testSel() {
         SqlSession session = MyBatisUtil.getSession();
 
         StudentMapper mapper = session.getMapper(StudentMapper.class);
 
         List<Student> list = mapper.selAll();
         for (Student student : list) {
             System.out.println(student);
         }
 
         session.close();
     }
     @Test
     public void testIns() {
         SqlSession session = MyBatisUtil.getSession();
 
         StudentMapper mapper = session.getMapper(StudentMapper.class);
 
         Student student = new Student();
         student.setName("小王");
         student.setAge(20);
         student.setGender("女");
         student.setCid(2);
 
         int num = mapper.insStu(student);
         if(num > 0) {
             System.out.println("ok");
             session.commit();
         } else {
             session.rollback();
         }
 
         session.close();
     }
     @Test
     public void testUpd() {
         SqlSession session = MyBatisUtil.getSession();
 
         StudentMapper mapper = session.getMapper(StudentMapper.class);
 
         int num = mapper.updStu(6, 30);
         if(num > 0) {
             System.out.println("ok");
             session.commit();
         } else {
             session.rollback();
         }
 
         session.close();
     }
     @Test
     public void testDel() {
         SqlSession session = MyBatisUtil.getSession();
 
         StudentMapper mapper = session.getMapper(StudentMapper.class);
 
         int num = mapper.delStu(6);
         if(num > 0) {
             System.out.println("ok");
             session.commit();
         } else {
             session.rollback();
         }
 
         session.close();
     }
 }

 package com.bjsxt.util;
 
 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;
 
 public class MyBatisUtil {
 
     private static SqlSessionFactory factory = null;
 
     static {
         try {
             InputStream is = Resources.getResourceAsStream("mybatis-cfg.xml");
             factory = new SqlSessionFactoryBuilder().build(is);
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 
     public static SqlSession getSession() {
         SqlSession session = null;
         if (factory != null) {
             // true表示开启自动提交
             // session = factory.openSession(true);
             session = factory.openSession();
         }
         return session;
     }
 }

 jdbc.driver=com.mysql.jdbc.Driver
 jdbc.url=jdbc:mysql://localhost:3306/java505
 jdbc.username=root
 jdbc.password=root

 # Set root category priority to INFO and its only appender to CONSOLE.
 log4j.rootCategory=ERROR, CONSOLE
 # log4j.rootCategory=DEBUG, CONSOLE, LOGFILE
 
 # 单独设置SQL语句的输出级别为DEBUG级别
 log4j.logger.com.bjsxt.mapper=DEBUG
 
 # CONSOLE is set to be a ConsoleAppender using a PatternLayout.
 log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
 log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
 log4j.appender.CONSOLE.layout.ConversionPattern=- %m%n
 
 # LOGFILE is set to be a File appender using a PatternLayout.
 log4j.appender.LOGFILE=org.apache.log4j.FileAppender
 log4j.appender.LOGFILE.File=d:/test.log
 log4j.appender.LOGFILE.Append=true
 log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
 log4j.appender.LOGFILE.layout.ConversionPattern=- %m %l%n

 <?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加载外部文件 -->
     <properties resource="db.properties" />
     <!-- settings标签 -->
     <settings>
         <!-- 设置MyBatis使用log4j日志支持 -->
         <setting name="logImpl" value="LOG4J"/>
     </settings>
     <!-- typeAliases给类型起别名 -->
     <typeAliases>
         <package name="com.bjsxt.pojo" />
     </typeAliases>
     <environments default="dev">
         <environment id="dev">
             <transactionManager type="JDBC" />
             <dataSource type="POOLED">
                 <property name="driver" value="${jdbc.driver}"/>
                 <property name="url" value="${jdbc.url}"/>
                 <property name="username" value="${jdbc.username}"/>
                 <property name="password" value="${jdbc.password}"/>
             </dataSource>
         </environment>
     </environments>
     <mappers>
         <package name="com.bjsxt.mapper" />
     </mappers>
 </configuration>