Create Couch Views in Spring

CouchDB is one of NoSQL database, uses JSON to store data, Javascript as its query language using MapReduce, and Http for an API.

Each document in db has a unique identifier (_id) and a revision(_rev) number.

CouchDB has a lots of benefits, I won’t list here :)

Import Couch in Project

We also import GOOGLE GSON package because we use it to transfer an object to json

dependencies {
  compile("org.lightcouch:lightcouch:0.1.8")
  runtime("org.lightcouch:lightcouch:0.1.8")
  compile("com.google.code.gson:gson:2.2.4")
  runtime("com.google.code.gson:gson:2.2.4")
}

Create a Factory Method of DbClient

import org.lightcouch.CouchDbClient;
import org.lightcouch.CouchDbProperties;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Component;

@Component
public class CouchDbClientFactory {
    @Autowired
    private ApplicationContext applicationContext;

    //@Value("${couchdb.createdb.if-not-exist}")
    protected boolean ifNotExist = true;
    @Value("${couchdb.username}")
    protected String username;
    @Value("${couchdb.password}")
    protected String password;
    @Value("${couchdb.host}")
    protected String host;
    @Value("${couchdb.protocol}")
    protected String protocol;
    @Value("${couchdb.port}")
    protected int port;

    public CouchDbClient getNewClientConnection(String dbName) {
        //super("application.properties");
        CouchDbProperties properties = new CouchDbProperties()
                .setDbName(dbName)
                .setCreateDbIfNotExist(ifNotExist)
                .setProtocol(protocol)
                .setHost(host)
                .setPort(port)
                .setUsername(username)
                .setPassword(password);
        CouchDbClient c = (CouchDbClient) applicationContext.getBean("couchDbClientConnection", properties);

        try {
            c.syncDesignDocsWithDb();
        } catch (NullPointerException n) {
            //I think this happends because there are no design documents specified.
        }
        return c;
    }
}

Use in Repository

@Repository
public class DemoRepository{

	@Autowired
	private CouchDbClientFactory dbClientFactory;

	public CouchDbClient dbClient;
	
	@PostConstruct
	private void setupViews() {
		init(); // Set up views here
	}
}

Couch view method

import java.util.HashMap;

import org.lightcouch.Document;

public class CouchView extends Document {
	private String language; 
	private HashMap<String,Object> views;
	
	public CouchView(String name) {
		this.setLanguage("javascript");
		this.setViews(null);
		String id = "_design/" + name; 
		this.setId(id); 
	}

	public String getLanguage() {
		return language;
	}

	public void setLanguage(String language) {
		this.language = language;
	}

	public HashMap<String,Object> getViews() {
		return views;
	}

	public void setViews(HashMap<String,Object> views) {
		this.views = views;
	}
}

Create Document Model

Model object can be stored in Couch

public class Job {

  private Long createdDate;
  private String parameterId; //your id
  private String username;
  
  //GETTERS and SETTERS here
}

Create views

1. Connect to database
2. Delete the view if it exists on startup

     try { 
    DesignDocument designDoc1 = dbClient.design().getFromDb("_design/jobs");
    dbClient.remove(designDoc1);
     } catch (NoDocumentException e) {/* that's ok, just continue */ }
   

3. Create views and save it to db

protected void init() {
    try {
        this.dbClient = dbClientFactory.getNewClientConnection("databaseName"));

        try {
            DesignDocument designDoc1 = dbClient.design().getFromDb("_design/jobs");
            dbClient.remove(designDoc1);
        } catch (NoDocumentException e) {/* that's ok, just continue */ }

        // recreate the view
        CouchView jobsView = new CouchView("jobs");
        HashMap<String, Object> views = new HashMap<String, Object>();
        HashMap<String, Object> processableJobsView = new HashMap<String, Object>();

        //byusername
        HashMap<String, Object> byUsername = new HashMap<String, Object>();
        byUsername.put("map", "function(job) { emit(job.username, job); }");
        views.put("byusername", byUsername);

        //bydate
        HashMap<String, Object> byCreatedDate = new HashMap<String, Object>();
        byCreatedDate.put("map",
                "function(job) { var currentTime=(new Date()).getTime(); "
                        + " var numberOfDays= Math.round ((currentTime-job.createdDate)/(1000*3600*24)); "
                        + " if(job.status != undefined && job.reportPath != undefined) { "
                        + "    emit( numberOfDays,job);"
                        + " } } "
        );
        views.put("bydate", byCreatedDate);

        HashMap<String, Object> allJobs = new HashMap<String, Object>();
        allJobs.put("map", "function(job) {  " +
                "if(job.status != undefined && job.reportPath != undefined){"
                + "emit( job.id,job);}} ");
        views.put("alljobs", allJobs);
        jobsView.setViews(views);
        this.dbClient.post(jobsView);
    } catch (DocumentConflictException ex) {
        // if this happens it means that the document was already created
    }
}

Use couch views

Couch privides metho to manipulate documents in it

public Job getJobById(String id) {

  Job j = this.dbClient.find(Job.class,id);
  return j;
}

public void deleteJobById(String id) {

  Job job = this.getJobById(id);
  try { deleteJobZipAttachement(job); } catch(Exception e) {} //if not found no problem

  JsonObject json = this.dbClient.find(JsonObject.class, id);
  this.dbClient.remove(json.get("_id").getAsString(), json.get("_rev").getAsString());
}

public Job getJobByGeneratedid(String id) {
  
  List<JsonObject> jsons = this.dbClient.view("jobs/bygeneratedid")
      .includeDocs(true)
      .key(id)
      .query(JsonObject.class);
  
  if(jsons == null || jsons.size()!=1) {
    throw new NoDocumentException("Failed to get exactly one document back by generated id");
  }
  
  return this.getJobById(jsons.get(0).get("_id").getAsString());
}