MyBatis（三、注解开发）

1、MyBatis的常用注解

       这几年来注解开发越来越流行，Mybatis也可以使用注解开发方式，这样我们就可以减少编写Mapper 映射文件了。

• @Insert：实现新增
  
• @Update：实现更新
  
• @Delete：实现删除
  
• @Select：实现查询
  
• @Result：实现结果集封装
  
• @Results：可以与@Result 一起使用，封装多个结果集
  
• @One：实现一对一结果集封装
  
• @Many：实现一对多结果集封装
  

2、MyBatis注解方式的增删改查

修改MyBatis的核心配置文件，我们使用了注解替代的映射文件，所以我们只需要加载使用了注解的Mapper接口即可。

  <!--加载映射关系-->

   <mappers>

       <!--指定接口所在的包-->

       <package name="com.xmp.mapper"></package>

   </mappers>

• 增
  

@Insert("insert into user values(#{id},#{username},#{password},#{birthday})")
publicvoidsave(Useruser);

• 删
  

@Update("update user set username=#{username},password=#{password} where id=#{id}")
publicvoidupdate(Useruser);

• 改
  

@Delete("delete from user where id=#{id}")
publicvoiddelete(intid);

• 查
  

@Select("select * from user where id=#{id}")
publicUserfindById(intid);
@Select("select * from user")
publicList<User>findAll();

3、MyBatis的注解实现复杂映射

实现复杂关系映射之前我们可以在映射文件中通过配置来实现，使用注解开发后，我们可以使用@Results注解 ，@Result注解，@One注解，@Many注解组合完成复杂关系的配置。

4、Mybatis注解开发步骤

1.导入maven依赖：

<dependencies>

   <!-- https://mvnrepository.com/artifact/org.objectweb.asm/org.objectweb.asm -->

   <dependency>

       <groupId>org.objectweb.asm</groupId>

       <artifactId>org.objectweb.asm</artifactId>

       <version>3.3.1.v201105211655</version>

   </dependency>

   <!-- https://mvnrepository.com/artifact/cglib/cglib -->

   <dependency>

       <groupId>cglib</groupId>

       <artifactId>cglib</artifactId>

       <version>3.2.8</version>

   </dependency>

   <!-- https://mvnrepository.com/artifact/commons-logging/commons-logging -->

   <dependency>

       <groupId>commons-logging</groupId>

       <artifactId>commons-logging</artifactId>

       <version>1.2</version>

   </dependency>

   <!-- https://mvnrepository.com/artifact/net.sf.ehcache/ehcache-core -->

   <dependency>

       <groupId>net.sf.ehcache</groupId>

       <artifactId>ehcache-core</artifactId>

       <version>2.6.11</version>

   </dependency>

   <!-- https://mvnrepository.com/artifact/org.javassist/javassist -->

   <dependency>

       <groupId>org.javassist</groupId>

       <artifactId>javassist</artifactId>

       <version>3.23.1-GA</version>

   </dependency>

   <!-- https://mvnrepository.com/artifact/junit/junit -->

   <dependency>

       <groupId>junit</groupId>

       <artifactId>junit</artifactId>

       <version>4.12</version>

       <scope>test</scope>

   </dependency>

   <!-- https://mvnrepository.com/artifact/log4j/log4j -->

   <dependency>

       <groupId>log4j</groupId>

       <artifactId>log4j</artifactId>

       <version>1.2.17</version>

   </dependency>

   <!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-api -->

   <dependency>

       <groupId>org.apache.logging.log4j</groupId>

       <artifactId>log4j-api</artifactId>

       <version>2.11.1</version>

   </dependency>

   <!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-core -->

   <dependency>

       <groupId>org.apache.logging.log4j</groupId>

       <artifactId>log4j-core</artifactId>

       <version>2.11.1</version>

   </dependency>

   <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->

   <dependency>

       <groupId>org.mybatis</groupId>

       <artifactId>mybatis</artifactId>

       <version>3.4.6</version>

   </dependency>

   <!-- https://mvnrepository.com/artifact/org.mybatis.caches/mybatis-ehcache -->

   <dependency>

       <groupId>org.mybatis.caches</groupId>

       <artifactId>mybatis-ehcache</artifactId>

       <version>1.1.0</version>

   </dependency>

   <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->

   <dependency>

       <groupId>mysql</groupId>

       <artifactId>mysql-connector-java</artifactId>

       <version>8.0.12</version>

   </dependency>

   <!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-log4j12 -->

   <dependency>

       <groupId>org.slf4j</groupId>

       <artifactId>slf4j-log4j12</artifactId>

       <version>1.8.0-beta2</version>

       <scope>test</scope>

   </dependency>

   <!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-api -->

   <dependency>

       <groupId>org.slf4j</groupId>

       <artifactId>slf4j-api</artifactId>

       <version>1.8.0-beta2</version>

   </dependency>

</dependencies>

2.数据库信息：

jdbc.driver=com.mysql.jdbc.Driverjdbc.url=jdbc:mysql://localhost:3306/mybatisjdbc.username=rootjdbc.passwords=root

3.编写日志配置文件:

##将等级为INFO的日志信息输出到stdout和R这两个目的

log4j.rootCategory=INFO, stdout , R  

#日志输出到控制台--   log4j.appender.stdout=org.apache.log4j.ConsoleAppender  

#日志布局样式-自定义样式

log4j.appender.stdout.layout=org.apache.log4j.PatternLayout  

#日志样式

log4j.appender.stdout.layout.ConversionPattern=[QC] %p [%t] %C.%M(%L) | %m%n  

##日志到每天一个日志文件    

log4j.appender.R=org.apache.log4j.DailyRollingFileAppender

##日志输出地址

log4j.appender.R.File=D:\\my.log  

#日志布局样式-自定义样式  

log4j.appender.R.layout=org.apache.log4j.PatternLayout  

#日志样式

1log4j.appender.R.layout.ConversionPattern=%d-[TS] %p %t %c - %m%n  

##下面是指定具体的包下面的所有日志的级别

log4j.logger.com.neusoft=DEBUG  

log4j.logger.com.opensymphony.oscache=ERROR  

log4j.logger.net.sf.navigator=ERROR  

log4j.logger.org.apache.commons=ERROR  

log4j.logger.org.apache.struts=WARN  

log4j.logger.org.displaytag=ERROR  

log4j.logger.org.springframework=DEBUG  

log4j.logger.com.ibatis.db=WARN  

log4j.logger.org.apache.velocity=FATAL  

4.编写配置文件：

SqlMapConfig.xml:

<?xmlversion="1.0"encoding="UTF-8"?><!DOCTYPEconfigurationPUBLIC"-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd"><configuration><propertiesresource="db.properties"></properties><settings><settingname="lazyLoadingEnabled"value="true"/><settingname="aggressiveLazyLoading"value="false"/><settingname="cacheEnabled"value="true"></setting></settings><typeAliases><!--别名--><!--<typeAliastype="com.xmp.entity.User"alias="user"></typeAlias>--><packagename="com.xmp..pojo"></package></typeAliases><environmentsdefault="development"><environmentid="development"><transactionManagertype="JDBC"></transactionManager><dataSourcetype="POOLED"><propertyname="driver"value="${jdbc.driver}"></property><propertyname="url"value="${jdbc.url}"></property><propertyname="username"value="${jdbc.username}"></property><propertyname="password"value="${jdbc.password}"></property></dataSource></environment></environments><mappers><!--<mapperresource="sqlmap/User.xml"></mapper>--><!--<mapperresource="mapper/UserMapper.xml"></mapper>--><!--Mapper接口和映射文件必须在同一文件夹下遵循规范<mapperclass="com.xmp..mapper.UserMapper"></mapper>--><!--Mapper接口的包名,自动扫描。遵循规范<packagename=""></package>--><packagename="com.xmp.mapper"></package><packagename="com.xmp.pojo"></package></mappers></configuration>

5.编写pojo类和Mapper接口:

@MapperpublicinterfaceUserMapper {
@Select("select * from user where id=#{id}")
publicUsergetUserById(Integerid);
@Delete("delete from user where id=#{id}")
publicvoiddeleteUserById(Integerid);
@Insert("insert user(id,username,birthday,sex,address) value(#{id},#{username},#{birthday},#{sex},#{address})")
publicvoidaddUser(Useruser);
@Update("update user set id=#{id},username=#{username},birthday=#{birthday},sex=#{sex},address=#{address} where id=#{id}")
publicvoidupdateUser(Useruser);
}

public class User {

   private int id;

   private String username;

   private Date birthday;

   private Integer sex;

   private String address;

   public int getId() {

       return id;

   }

   public void setId(int id) {

       this.id = id;

   }

   public String getUsername() {

       return username;

   }

   public void setUsername(String username) {

       this.username = username;

   }

   public Date getBirthday(Date date) {

       return birthday;

   }

   public void setBirthday(Date birthday) {

       this.birthday = birthday;

   }

   public Integer getSex() {

       return sex;

   }

   public void setSex(Integer sex) {

       this.sex = sex;

   }

   public String getAddress() {

       return address;

   }

   public void setAddress(String address) {

       this.address = address;

   }

   @Override

   public String toString() {

       return "User{" +

               "id=" + id +

               ", username='" + username + '\'' +

               ", birthday=" + birthday +

               ", sex=" + sex +

               ", address='" + address + '\'' +

               '}';

   }

}

6.编写测试类:

public class UserMapperTest {

   SqlSessionFactory sqlSessionFactory;

   @Before

   public void setUp() throws Exception {

       InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");

       //初始化mybatis,创建SqlSessionFactory类的实例

       sqlSessionFactory =  new SqlSessionFactoryBuilder().build(resourceAsStream);

   }

@TestpublicvoidgetUserById() {
SqlSessionsqlSession=sqlSessionFactory.openSession();
UserMapperuserMapper=sqlSession.getMapper(UserMapper.class);
UseruserById=userMapper.getUserById(10);
System.out.println("Message="+userById);
    }

@TestpublicvoiddeleteUserById() {
SqlSessionsqlSession=sqlSessionFactory.openSession();
UserMapperuserMapper=sqlSession.getMapper(UserMapper.class);
userMapper.deleteUserById(26);
    }

@TestpublicvoidaddUser() {
SqlSessionsqlSession=sqlSessionFactory.openSession();
UserMapperuserMapper=sqlSession.getMapper(UserMapper.class);
Useruser=newUser();
user.setId(30);
user.setUsername("xmp");
user.setBirthday(newDate());
user.setAddress("SH");
userMapper.addUser(user);
sqlSession.commit();
    }

@TestpublicvoidupdateUser() {
SqlSessionsqlSession=sqlSessionFactory.openSession();
UserMapperuserMapper=sqlSession.getMapper(UserMapper.class);
UseruserById=userMapper.getUserById(1);
userById.setBirthday(newDate());
userById.setAddress("广西柳州");
userMapper.updateUser(userById);
sqlSession.commit();
    }

}