MyBatis学习（五）

视频观看地址：http://edu.51cto.com/course/14674.html?source=so

1、动态sql

1.1、if

需求：查询全部用户，如果用户填写了姓名，按照姓名的模糊查询，如果用户填写了姓名和年龄，则按姓名和年龄一起查找

1、接口定义

public List querybyUser(User vo) throws Exception;

2、mapper.xml配置

    select * from tb_user where 1=1
    
       and user_Name like #{userName}
    
    
        and age =#{age}
    
  

3、测试方法

@Test
    public void testIf()throws Exception{
        User user = new User();
        user.setUserName(null);
        user.setAge(17);
        List list = userMapper.querybyUser(user);
        for (User u : list) {
            System.out.println(u);
        }
    }

4、日志

DEBUG - Opening JDBC Connection
DEBUG - Created connection 276327391.
DEBUG - Setting autocommit to false on JDBC Connection [oracle.jdbc.driver.T4CConnection@10786bdf]
DEBUG - ==>  Preparing: select * from tb_user where 1=1 and age =? 
DEBUG - ==> Parameters: 17(Integer)
DEBUG - <==      Total: 1
User [userid=10, userName=阿珂3, pwd=123456, age=17, sex=女, birthday=Mon Aug 13 14:57:50 CST 2018]
DEBUG - Resetting autocommit to true on JDBC Connection [oracle.jdbc.driver.T4CConnection@10786bdf]
DEBUG - Closing JDBC Connection [oracle.jdbc.driver.T4CConnection@10786bdf]
DEBUG - Returned connection 276327391 to pool.

1.2、where

在前面的sql中的我们认为的定义了一个where 1=1这样的东西，此时我们可以通过mybatis的where标签来搞定

    select * from tb_user 
    
        
            and user_Name like #{userName}
        
        
            and age =#{age}
        
    

  

where :自动根据需求生成，并且可以剔除不需要and

直接测试即可

1.3、foreach

另外一个动态 SQL 通用的必要操作是迭代一个集合, 通常是构建在 IN 条件中的。

接口方法定义

public List querybyIn(QueryUser vo) throws Exception;

mapper.xml

        select * from tb_user
        
            
                
                
                    #{userid}
                
            
        
  

测试方法

@Test
    public void testforeach()throws Exception{
        QueryUser queryUser= new QueryUser();
        queryUser.setUserids(new int[]{8,9,2,3});
        List list = userMapper.querybyIn(queryUser);
        for (User u : list) {
            System.out.println(u);
        }
    }

日志

DEBUG - Opening JDBC Connection
DEBUG - Created connection 1060925979.
DEBUG - Setting autocommit to false on JDBC Connection [oracle.jdbc.driver.T4CConnection@3f3c721b]
DEBUG - ==>  Preparing: select * from tb_user WHERE userid in ( ? , ? , ? , ? ) 
DEBUG - ==> Parameters: 8(Integer), 9(Integer), 2(Integer), 3(Integer)
DEBUG - <==      Total: 4
User [userid=8, userName=阿珂, pwd=123456, age=18, sex=女, birthday=Mon Aug 13 14:06:14 CST 2018]
User [userid=9, userName=阿珂2, pwd=123456, age=18, sex=女, birthday=Mon Aug 13 14:56:45 CST 2018]
User [userid=2, userName=张三, pwd=123456, age=10, sex=男, birthday=Mon Aug 13 10:07:55 CST 2018]
User [userid=3, userName=李四, pwd=123456, age=10, sex=男, birthday=Mon Aug 13 10:07:55 CST 2018]
DEBUG - Resetting autocommit to true on JDBC Connection [oracle.jdbc.driver.T4CConnection@3f3c721b]
DEBUG - Closing JDBC Connection [oracle.jdbc.driver.T4CConnection@3f3c721b]
DEBUG - Returned connection 1060925979 to pool.

1.4、Set

set 元素可以被用于动态包含更新的列,而不包含不需更新的(动态更新)

接口定义

public int dycUpdate(User vo) throws Exception;

mapper.xml定义

    update tb_user
    
        
            user_name=#{userName},
        
        
            pwd=#{pwd},
        
        
            age=#{age},
        
        
            sex=#{sex},
        
        
            birthday=#{birthday},
        
    
    where userid=#{userid}
  

测试方法

@Test
    public void testdycUpdate()throws Exception{
        User user = new User();
        user.setUserName("hello");
        user.setSex("男");
        user.setBirthday(new Date());
        user.setUserid(8);
        userMapper.dycUpdate(user);
        sqlSession.commit();
    }

日志

DEBUG - Opening JDBC Connection
DEBUG - Created connection 340839523.
DEBUG - Setting autocommit to false on JDBC Connection [oracle.jdbc.driver.T4CConnection@1450cc63]
DEBUG - ==>  Preparing: update tb_user SET user_name=?, sex=?, birthday=? where userid=? 
DEBUG - ==> Parameters: hello(String), 男(String), 2018-08-14 10:19:19.311(Timestamp), 8(Integer)
DEBUG - <==    Updates: 1
DEBUG - Committing JDBC Connection [oracle.jdbc.driver.T4CConnection@1450cc63]
DEBUG - Resetting autocommit to true on JDBC Connection [oracle.jdbc.driver.T4CConnection@1450cc63]
DEBUG - Closing JDBC Connection [oracle.jdbc.driver.T4CConnection@1450cc63]
DEBUG - Returned connection 340839523 to pool.

1.5、动态添加

接口定义

public int dycInsert(User vo) throws Exception;

mapper.xml文件

 
        insert into tb_user (
                userid,
                
                    
                        user_name,
                    
                    
                        pwd,
                    
                    
                        age,
                    
                    
                        sex,
                    
                    
                        birthday,
                    
                

        ) values(
            seq_user.nextval,
            
                
                #{userName},
                
                
                    #{pwd},
                
                
                    #{age},
                
                
                    #{sex},
                
                
                    #{birthday},
                
            

        )   
  

测试方法

@Test
    public void testdycInsert()throws Exception{
        User user = new User();
        user.setUserName("yui");
        user.setSex("男");
        user.setBirthday(new Date());
        user.setUserid(8);
        userMapper.dycInsert(user);
        sqlSession.commit();
    }

日志

DEBUG - Opening JDBC Connection
DEBUG - Created connection 1341177488.
DEBUG - Setting autocommit to false on JDBC Connection [oracle.jdbc.driver.T4CConnection@4ff0be90]
DEBUG - ==>  Preparing: insert into tb_user ( userid, user_name, sex, birthday ) values( seq_user.nextval, ?, ?, ? ) 
DEBUG - ==> Parameters: yui(String), 男(String), 2018-08-14 10:31:06.973(Timestamp)
DEBUG - <==    Updates: 1
DEBUG - Committing JDBC Connection [oracle.jdbc.driver.T4CConnection@4ff0be90]
DEBUG - Resetting autocommit to true on JDBC Connection [oracle.jdbc.driver.T4CConnection@4ff0be90]
DEBUG - Closing JDBC Connection [oracle.jdbc.driver.T4CConnection@4ff0be90]
DEBUG - Returned connection 1341177488 to pool.

1.6、choose、when、otherwise

有时我们不想应用所有的条件, 相反我们想选择很多情况下的一种。 Java 中的 switch 和 语句相似,MyBatis 提供 choose 元素。

需求：查询所有用户

1.如果用户填写了性别和姓名，则按姓名查找

2.如果用户填写了姓名，按姓名查找

3.如果用户未填写姓名，但是填写了性别，则按性别查找

接口声明

public List queryDyc(QueryUser vo) throws Exception;

mapper.xml文件

        select * from tb_user
        
            
                
                    user_name=#{name}
                
                
                    sex=#{sex}
                
                
                    age>5
                
            
        
  

测试方法

@Test
    public void testIfelse()throws Exception{

        QueryUser queryUser= new QueryUser();
        queryUser.setName(null);
        queryUser.setSex(null);
        List list = userMapper.queryDyc(queryUser);
        for (User u : list) {
            System.out.println(u);
        }
    }

日志

DEBUG - Opening JDBC Connection
DEBUG - Created connection 480779844.
DEBUG - Setting autocommit to false on JDBC Connection [oracle.jdbc.driver.T4CConnection@1ca81e44]
DEBUG - ==>  Preparing: select * from tb_user WHERE age>5 
DEBUG - ==> Parameters: 
DEBUG - <==      Total: 7
User [userid=8, userName=hello, pwd=123456, age=18, sex=男, birthday=Tue Aug 14 10:19:19 CST 2018]
User [userid=9, userName=阿珂2, pwd=123456, age=18, sex=女, birthday=Mon Aug 13 14:56:45 CST 2018]
User [userid=10, userName=阿珂3, pwd=123456, age=17, sex=女, birthday=Mon Aug 13 14:57:50 CST 2018]
User [userid=2, userName=张三, pwd=123456, age=10, sex=男, birthday=Mon Aug 13 10:07:55 CST 2018]
User [userid=3, userName=李四, pwd=123456, age=10, sex=男, birthday=Mon Aug 13 10:07:55 CST 2018]
User [userid=4, userName=王五, pwd=123456, age=10, sex=男, birthday=Mon Aug 13 10:07:55 CST 2018]
User [userid=5, userName=赵六, pwd=123456, age=10, sex=男, birthday=Mon Aug 13 10:07:55 CST 2018]
DEBUG - Resetting autocommit to true on JDBC Connection [oracle.jdbc.driver.T4CConnection@1ca81e44]
DEBUG - Closing JDBC Connection [oracle.jdbc.driver.T4CConnection@1ca81e44]
DEBUG - Returned connection 480779844 to pool.

1.7、sql片段

sql片段是为了将一些常用的sql语句保存起来，在需要的时候进行引用即可

如果sql片段和statement在同一个命名空间下，则直接引用

 
        select * from tb_user
  
  
        
        
            
                
                    user_name=#{name}
                
                
                    sex=#{sex}
                
                
                    age>5
                
            
        
  

如果sql片段和statement不在同一个命名空间下，则直接则使用命名空间.sqlid的形式进行引用

 
        
        
            
                
                    user_name=#{name}
                
                
                    sex=#{sex}
                
                
                    age>5