Param Condition Control ​

Syntax reference:【Beetl-Condition Control】 Due to the difference in configuration of Beetl in ngbatis, the <% %> will be replaced by @ \n, for example：

- <%if ( aBool ) { 
-                         
- } %>                
+ @if ( aBool ) {
+                       
+ @}

Use of Ternary Expressions ​

• PersonDao.java

  java

  Person selectByNameIfNotEmpty( String name );

• PersonDao.xml

  xml

  <select id="selectByNameIfNotEmpty">
          MATCH (n: person)
          WHERE 1 == 1 
          ${ isEmpty( p0 ) ? '' : 'AND n.person.name == $p0' }
          RETURN n
          LIMIT 1
      </select>

Use of if ​

• PersonDao.java

  java

  // params = { age: 18 }
      Person selectByNameAndAge( Person person, Map<String, Object> params );

• PersonDao.xml

  xml

  <select id="selectByNameAndAge">
        MATCH (n: person)
        WHERE 1 == 1
        @if ( isNotEmpty( $p0.name ) ) {
          AND n.person.name == $p0.name
        @}
        @if ( isNotEmpty( $p1.age ) ) {
          AND n.person.age > $p1.age
        @}
        RETURN n
        LIMIT 1
    </select>

Use of if-else ​

• PersonDao.java

  java

  // org.springframework.data.repository.query.Param
      Person selectMarriageable( @Param("gender") String gender );

• PersonDao.xml

  xml

  <select id="selectMarriageable">
          MATCH (n: person)
          WHERE 1 == 1 
          @if ( gender == 'F' ) {
            AND n.person.age >= 20
          @} else {
            AND n.person.age >= 22
          @}
          RETURN n
          LIMIT 1
      </select>

Use of switch-case ​

• PersonDao.java

  java

  // org.springframework.data.repository.query.Param
      Person selectMarriageable( @Param("gender") String gender );

• PersonDao.xml

  xml

  <select id="selectMarriageable">
          MATCH (n: person)
          WHERE 1 == 1 
          @switch( gender ){
          @   case 'F':
                  AND n.person.age >= 20  
          @     break;
          @   case 'M':
                  AND n.person.age >= 22
          @     break;
          @   default:
                  AND n.person.age >= 24
          @}
          RETURN n
          LIMIT 1
      </select>

• Attention: the switch variable placed here cannot be null

Use of select case ​

• PersonDao.java

  java

  // org.springframework.data.repository.query.Param
      Person selectByGender( @Param("gender") String gender );

• PersonDao.xml

  xml

  <select id="selectMarriageable">
          MATCH (n: person)
          WHERE 1 == 1 
          @select( gender ){
          @   case 'F', 'M':
                  AND n.person.gender is not null
          @   default:
                  AND n.person.gender is null
          @}
          RETURN n
          LIMIT 1
      </select>

Use of decode ​

• PersonDao.java

  java

  // org.springframework.data.repository.query.Param
      Person selectMarriageable( @Param("gender") String gender );

• PersonDao.xml

  xml

  <select id="selectMarriageable">
          MATCH (n: person)
          WHERE 1 == 1 
          ${ decode( gender, 
            "F", "AND n.person.age >= 20", 
            "M", "AND n.person.age >= 22", 
            "AND n.person.age >= 24" 
          ) }
          RETURN n
          LIMIT 1
      </select>

Conclusion ​

At this time, the methods that can be used for condition control are basically introduced. Judgment can only be made when inputting parameters. The return value cannot be controlled by conditions.