将结果集映射到复杂的json结构

Question

I am developing an application using spring boot and MySQL. I am also using JDBCTemplate to interact with database from spring boot application.

In the specific case, I am calling a stored procedure which returns the resultset as like below: (example data)

Cluster         AppType      Application
-----------------------------------------
C1               AT1            A
C1               AT1            B
C1               AT2            A
C1               AT2            B

I am mapping this result to pojo as like below:

Repository:

public List<UserSubHierarchy> getUserHierarchy() {
            List<UserSubHierarchy> listCount = new LinkedList<>();
            String sql = "   call GET_USER_SUBHIERARCHY()";

            listCount = jdbcTemplate.query(sql, new BeanPropertyRowMapper<UserSubHierarchy>(UserSubHierarchy.class));

            return listCount;
    }

Pojo:

public class UserSubHierarchy {
    private String apm_buisness_cluster;
    private String apm_application_type;
    private String apm_application_name;
     // setter and getter
}

After this I need to process the List<UserSubHierarchy> and bring the output as follows:

[
   {
      "text":"C1",
      "children":[
         {
            "text":"AT1",
            "children":[
               {
                  "text":"A",
                  "children":null
               },
               {
                  "text":"B",
                  "children":null
               }
            ]
         },
         {
            "text":"AT2",
            "children":[
               {
                  "text":"A",
                  "children":null
               },
               {
                  "text":"B",
                  "children":null
               }
            ]
         }
      ]
   }
]

For the above JSON format I have created pojo as like below:

public class AppList{
private String text;
private List<AppList> children;
//getter and setter
}

I have tried for last two days, I couldn't bring my expected output. Kindly help me or guide me to get the solution. I guess I am clearly mentioning all my resources, if not kindly let me know. Thanks all in Advance.

Answer 1

For collecting the items into a map structure you can do something like this:

final Map<String, Map<String, List<UserSubHierarchy>>> out = list.stream().collect(
          Collectors.groupingBy(UserSubHierarchy::getApm_buisness_cluster,
          Collectors.groupingBy(UserSubHierarchy::getApm_application_type)));

This gives back the following data:

{C1={
  AT1=[
    WIMdataReader$UserSubHierarchy@7a79be86, 
    WIMdataReader$UserSubHierarchy@34ce8af7], 
  AT2=[
    WIMdataReader$UserSubHierarchy@b684286, 
    WIMdataReader$UserSubHierarchy@880ec60]}}

If your data has a fixed structure like the data above then you can skip the children item labels and just have encode the map as it is, using whatever JSON library you prefer, giving output like this:

{  
   "C1":{  
      "AT1":[  
         "A",
         "B"
      ],
      "AT2":[  
         "A",
         "B"
      ]
   }
}

Full test code

public class WIMdataReader {
  public static class UserSubHierarchy {
    private String buisnessCluster;
    private String applicationType;
    public String getBuisnessCluster() {
      return buisnessCluster;
    }
    public String getApplicationType() {
      return applicationType;
    }
    private String applicationName;
    public UserSubHierarchy(String buisnessCluster, String applicationType, String applicationName) {
      this.buisnessCluster = buisnessCluster;
      this.applicationType = applicationType;
      this.applicationName = applicationName;
    }
    @Override
    public String toString() {
      return applicationName;
    }
  }
  private static final List<UserSubHierarchy> list = List.of(
      new UserSubHierarchy("C1", "AT1", "A"),
      new UserSubHierarchy("C1", "AT1", "B"),
      new UserSubHierarchy("C1", "AT2", "A"),
      new UserSubHierarchy("C1", "AT2", "B")
  );
  public static void main(final String... args) {
    final Map<String, Map<String, List<UserSubHierarchy>>> out =
        list.stream().collect(
            Collectors.groupingBy(UserSubHierarchy::getBuisnessCluster,
            Collectors.groupingBy(UserSubHierarchy::getApplicationType)));
    System.out.println(out);
  }
}

Output: {C1={AT1=[A, B], AT2=[A, B]}}