[map] universal map usage & two ways of fuzzy query

Omnipotent Map

• Map You can pass any number of parameters , Object must pass all parameters

• For two parameters Map perhaps annotation

• Map structure ： Key value pair

• purpose ： Suppose our entity class , Or a table in a database , Too many fields or parameters , We'll consider using Map

• Map Pass parameters , Take it directly from the parameter Key that will do ,Key It can be different from the attribute name in the database

UserMapper(or UserDao).java

// Omnipotent Map
int addUser1(Map<String,Object> map);

UserMapper.xml

• #{userid} Medium Userid It can be compared with the table in the database id The names are different , Because this is the key

    <!-- Omnipotent Map Map Medium key You can take it out ,Map You can pass any parameter , Object must pass all parameters -->
    <insert id="addUser1" parameterType="map">
        INSERT INTO mybatis.`user`(id,NAME,pwd) VALUES(#{userid},#{userName},#{password})
    </insert>

UserMapperTest.java

•     map.put("userid", 5);
      map.put("userName", "byby");
  

  Here, you can only pass two parameter values to the database

    /*  Omnipotent Map test  Map You can pass any parameter , Object must pass all parameters  */
    @Test
    public void adduser1(){
    
        // obtain sqlsession
        SqlSession sqlSession = MyBatisUtils.getSqlSession();

        // Get UserMapper example 
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        // Put the test value into the example 
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("userid", 5);
        map.put("userName", "byby");
// map.put("password", "2124");
        // Call test methods 
        userMapper.addUser1(map);

        // Additions and deletions , Commit transaction 
        sqlSession.commit();
        // close sqlsession
        sqlSession.close();

    }

test result ：

• No parameter value passed , The password for Null

There are two ways of fuzzy query

There are two methods of fuzzy query ：

1. Java When the code executes , Pass wildcard % %

   UserMapper.java

       // Fuzzy query 
       List<User> getUserLike(String value);
   

   UserMapper.xml

   <!-- Fuzzy query -->
   <select id="getUserLike" parameterType="String" resultType="com.kuang.pojo.User">
       select * from mybatis.user where name like #{value}
   </select>
   

   UserMapperTest.java

       /*  Fuzzy query   Name input “ Li ”, You can find all name contains “ Li ” Information about   Pass in the parameter ： String value  Return results  List<User> */
       @Test
       public void getUserLike(){
         
           // obtain SqlSession
           SqlSession sqlSession = MyBatisUtils.getSqlSession();
   
           // Get UserMapper example 
           UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
           
           // Pass the test value into the instance 
           List<User> userList = userMapper.getUserLike("% Zhang %");
   
           // Print out userList
           for (User user : userList) {
         
               System.out.println(user);
           }
   
           // close SqlSession
           sqlSession.close();
   
       }
   

2. stay sql Using wildcards in stitching

   UserMapper.java

   // Fuzzy query 
   List<User> getUserLike(String value);
   

   UserMapper.xml

   <select id="getUserLike" parameterType="String" resultType="com.kuang.pojo.User">
       select * from mybatis.user where name like "%"#{value}"%"
   </select>
   

   UserMapperTest.java

   // Pass the test value into the instance 
   List<User> userList = userMapper.getUserLike(" Zhang ");
   

Sql Inject

sql Inject ：
select * from mybatis.user where id = ?
select * from mybaits.user where id = 1 or 1=1
 The original user needs to pass a id Parameters , But the user spliced one when delivering to the back end  or 1=1, At this time, users can query the information of all users , This results in sql Inject 
 therefore , During the query , Will pass #{value} To write death , The parameters passed to the back end cannot be spliced 
 When fuzzy query, try to Mapper.xml Write the parameters passed in , Do not splice , Fuzzy matching matches in the test code