Djolar for MyBatis

Introduction

Djolar is a protocol like graphql, but only focus on how to filter data in database. It is very common to use multiple filter in web-app or mobile-app, Djolar is lifesaver to build clean API services, unified frontend component.

For example, we need to search a user with

• name equal to enix,
• age greater than 18

so we can invoke the api with the following query parameters:

http://localhost:8000/api/v1/users?q=name__eq__enix|age__gt__18

q stand for query, the query value syntax as below:

q-value := <filter-clause1>[|<filter-clause2>|...] 
filter-clause := <field-name>__<operator>__<filter-value>

support operators:

operator	stands for
eq	equal (=)
gt	greater than (>)
ge	greater than or equal (>=)
lt	less than (<)
le	less than or equal (<=)
co	contain (LIKE)
sw	starts with (LIKE)
ew	ends with (LIKE)
in	in (IN)
nn	is not null
nu	is null

1. Installation

<dependency>
  <groupId>com.enixyu</groupId>
  <artifactId>djolar-mybatis</artifactId>
  <version>${latest.version}</version>
</dependency>

2. Usage

1. Setup interceptor for mybatis

   <plugins>
     <!-- other interceptors -->
     ...
     <plugin interceptor="com.enixyu.djolar.mybatis.plugin.DjolarInterceptor">
       <!-- dialect for build sql query -->
       <property name="dialect" value="mysql=com.enixyu.djolar.mybatis.dialect.MySQLDialect"/>
       <!-- throw exception if field not found in mapping, possible values: true, false -->
       <property name="throw-if-field-not-found" value="true"/>
       <!-- throw exception if operator not supported, possible values: true, false -->
       <property name="throw-if-operator-not-support" value="true"/>
     </plugin>
   </plugins>

2. Define mapper interface

   @Mapper
   // Specify the mapping class
   @Mapping(Blog.class)
   public interface BlogMapper {
   
     // DjolarInterceptor only handle method with QueryRequest as parameter
     List<Blog> findAll(QueryRequest request);
   
     Blog findById(int id);
   
     // Override the mapping class defined in class level
     @Mapping(BlogDjolarMapping.class)
     List<Blog> findBlogWithUser(QueryRequest request);
   }

3. Define the mapper xml

   <mapper namespace="com.enixyu.djolar.mybatis.mapper.BlogMapper">
     ...
   
     <select id="findAll" resultType="com.enixyu.djolar.mybatis.domain.Blog">
       SELECT * FROM `blog`
     </select>
   
     <select id="findBlogWithUser" resultType="com.enixyu.djolar.mybatis.domain.Blog">
       SELECT `blog`.* FROM `blog`
       INNER JOIN `user` ON `blog`.`user_id` = `user`.`id`
     </select>
   
     ...
   </mapper>

4. Client make query

   public class Test {
   
     @Test
     public void testDjolarIntegerEqual() {
       try (SqlSession session = this.sessionFactory.openSession()) {
         BlogMapper mapper = session.getMapper(BlogMapper.class);
         QueryRequest request = new QueryRequest();
         // Get the records with `id` column equal to `1`
         request.setQuery("id__eq__1");
         List<Blog> results = mapper.findAll(request);
         Assertions.assertEquals(1, results.size());
       }
     }
   }

Release Note

v1.8.5

1. Handle invalid expression value when parsing expression, throw exception if flag KEY_THROW_IF_EXPRESSION_INVALID is on.

v1.8.4

1. Ignore query with empty string, without throwing expression invalid exception.

v1.8.3

1. Return a false where clause (1 = 0) for invalid operator, invalid expression, mapping field not found if plugin parameters are set to false.
2. Fix sort clause without using the tableName issue.
3. Add more test cases.

v1.8.2

1. Add a plugin parameter throw-if-expression-invalid to control whether throw exception if expression is invalid.
2. Set default value of all plugin parameters to false (Since expression is typically passed from frontend, the backend does not know the expression in advance).

v1.8.1

1. Fix interceptor crash when QueryRequest parameter is null issue.

v1.8.0

1. Support mapper method with multiple parameters including QueryRequest parameter.

v1.7.5

1. Add plugin property (throw-if-field-not-found) for user to decide whether throw exception if query field not found.
2. Add plugin property (throw-if-operator-not-support) for user to decide whether throw exception if operator not supported.

v1.7.2

1. Support QueryRequest subclass as mapper parameter.
2. Remove multiple parameters support.

v1.7.1

1. Fix no-parameter mapper method crash issue.

v1.7.0

1. Support customize dialect class.
2. Support mapper method with multiple parameters including QueryRequest parameter.

v1.6.1

• Throw DjolarParserException if sort field not found in query mapping.

v1.6.0

• Throw DjolarParserException if query field not found in query mapping
• Throw DjolarParserException if operator is not supported

v1.4.1

• Fix parser failed to parse value when mapping class using boxed type
• Reorganize the benchmark codes
• Upgrade maven version

v1.4.0

• Support in and not in operators

  public class Test {
    @Test
    void testCollectionIn() {
      try (SqlSession session = this.sessionFactory.openSession()) {
        BlogMapper mapper = session.getMapper(BlogMapper.class);
        QueryRequest request = new QueryRequest();
        // in operator
        request.setQuery("id__in__1,2,3");
        List<Blog> results = mapper.findAll(request);
        Assertions.assertEquals(2, results.size());
  
        // not in operator
        request.setQuery("id__ni__1,2,3");
        List<Blog> results = mapper.findAll(request);
        Assertions.assertEquals(2, results.size());
      }
    }
  }

• Fix issue when query with multiple same db field, e.g., two filter statement with id field int the following query clause

  id__gt__1|n__sw__abc|id__lt__11
  

v1.3.0

• add is null and is not null operators

  public class Test {
    void test() {
      // filter with blog name is not null
      QueryRequest request = new QueryRequest();
      request.setQuery("blog_name__nn");
      List<Blog> results = mapper.findBlogWithUser(request);
      
      // filter with blog name is null
      request.setQuery("blog_name__nu");
      List<Blog> results = mapper.findBlogWithUser(request);
    }
  } 

v1.2.0

• support additional filter and sort in mapper method

  @Mapper
  @Mapping(Blog.class)
  public interface BlogMapper {
    // force to filter user_id equal to 1 
    @AdditionalWhere(where = "user_id__eq__1")
    // force to sort by "id" desc and "name" asc
    @AdditionalSort(sort = "-id,name")
    List<Blog> findMyBlogs(QueryRequest request);
  }

v1.1.0

• add request field builder

v1.0.0

• implement djolar spec

Djolar implementation for other language

• djolar for golang
• djolar for python django