Spring Data MongoDB – Auto Sequence ID example

mkyong

In this tutorial, we will show you how to generate an auto-incrementing sequence id in MongoDB + Spring Data environment.

Tools used in this project :

1. Spring Data MongoDB 1.2.1.RELEASE
2. MongoDB 2.4.5
3. Eclipse 4.2
4. Maven 3

At the end of this tutorial, if the collection name “hosting” is saved, a new auto-incrementing sequence id will be assigned. Below is the Java code snippet to generate the sequence id.

 public long getNextSequenceId(String key) {
 Query query = new Query(Criteria.where("_id").is(key));
 Update update = new Update();
 update.inc("seq", 1);
 FindAndModifyOptions options = new FindAndModifyOptions();
 options.returnNew(true);
 SequenceId seqId = 
 mongoOperation.findAndModify(query, update, options, SequenceId.class);
 return seqId.getSeq();
 } 

1. Project Structure

Review the project directory structure, a standard Maven project.

2. Maven Pom

In case you are interested at the project dependencies.

pom.xml

 
 1.6
 3.2.2.RELEASE
 2.11.1
 1.2.1.RELEASE
 
 
 
 
 org.springframework
 spring-core
 ${spring.version}
 
 
 
 cglib
 cglib
 2.2.2
 
 
 
 org.springframework.data
 spring-data-mongodb
 ${springdata.version}
 
 
 
 org.mongodb
 mongo-java-driver
 ${mongojavadriver.version}
 
 
 
 SpringData
 
 
 org.apache.maven.plugins
 maven-compiler-plugin
 2.3.2
 
 ${jdk.version}
 ${jdk.version}
 
 
 
 

3. Sequence Collection

We create a collection name “sequence” to store the auto increase sequence id. Refer to the SequenceDaoImpl.java below, it shows you the code to generate the sequence id.

Note
Create the “sequence” collection in your MongoDB first!

 db.sequence.insert({_id: "hosting",seq: 0})

SequenceId.java

package com.mkyong.seq.model;
import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;
@Document(collection = "sequence")
public class SequenceId {
 @Id
 private String id;
 private long seq;
 //get, set, toString...
}

SequenceDao.java

package com.mkyong.seq.dao;
import com.mkyong.seq.exception.SequenceException;
public interface SequenceDao {
 long getNextSequenceId(String key) throws SequenceException;
}

SequenceDaoImpl.java

package com.mkyong.seq.dao;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.mongodb.core.FindAndModifyOptions;
import org.springframework.data.mongodb.core.MongoOperations;
import org.springframework.data.mongodb.core.query.Criteria;
import org.springframework.data.mongodb.core.query.Query;
import org.springframework.data.mongodb.core.query.Update;
import org.springframework.stereotype.Repository;
import com.mkyong.seq.exception.SequenceException;
import com.mkyong.seq.model.SequenceId;
@Repository
public class SequenceDaoImpl implements SequenceDao {
 @Autowired
 private MongoOperations mongoOperation;
 @Override
 public long getNextSequenceId(String key) throws SequenceException {
 
 //get sequence id
 Query query = new Query(Criteria.where("_id").is(key));
 //increase sequence id by 1
 Update update = new Update();
 update.inc("seq", 1);
 //return new increased id
 FindAndModifyOptions options = new FindAndModifyOptions();
 options.returnNew(true);
 //this is the magic happened.
 SequenceId seqId = 
 mongoOperation.findAndModify(query, update, options, SequenceId.class);
 //if no id, throws SequenceException
 //optional, just a way to tell user when the sequence id is failed to generate.
 if (seqId == null) {
 throw new SequenceException("Unable to get sequence id for key : " + key);
 }
 return seqId.getSeq();
 }
}

SequenceException.java

package com.mkyong.seq.exception;
public class SequenceException extends RuntimeException {
 private static final long serialVersionUID = 1L;
 private String errCode;
 private String errMsg;
 //get, set...
 public SequenceException(String errMsg) {
 this.errMsg = errMsg;
 }
}

4. Get the Sequence ID

To get the sequence id, uses sequenceDao.getNextSequenceId("key").

HostingBo.java

package com.mkyong.hosting.bo;
import com.mkyong.seq.exception.SequenceException;
public interface HostingBo {
 void save(String name) throws SequenceException;
}

HostingBoImpl.java

package com.mkyong.hosting.bo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.mkyong.hosting.dao.HostingDao;
import com.mkyong.hosting.model.Hosting;
import com.mkyong.seq.dao.SequenceDao;
import com.mkyong.seq.exception.SequenceException;
@Service
public class HostingBoImpl implements HostingBo {
 private static final String HOSTING_SEQ_KEY = "hosting";
 @Autowired
 private SequenceDao sequenceDao;
 @Autowired
 private HostingDao hostingDao;
 @Override
 public void save(String name) throws SequenceException {
 Hosting hosting = new Hosting();
 hosting.setId(sequenceDao.getNextSequenceId(HOSTING_SEQ_KEY));
 hosting.setName(name);
 hostingDao.save(hosting);
 System.out.println(hosting);
 }
}

5. Testing

Run a simple test.

package com.mkyong;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import com.mkyong.config.AppConfig;
import com.mkyong.hosting.bo.HostingBo;
import com.mkyong.seq.exception.SequenceException;
public class App {
 public static void main(String[] args) {
 ApplicationContext ctx = 
 new AnnotationConfigApplicationContext(AppConfig.class);
 HostingBo hostingBo = (HostingBo) ctx.getBean("hostingBoImpl");
 try {
 hostingBo.save("cloud.google.com");
 hostingBo.save("heroku.com");
 hostingBo.save("cloudbees.com");
 } catch (SequenceException e) {
 System.out.println(e.getErrMsg());
 }
 }
}

Output – Java console

Hosting [id=1, name=cloud.google.com]
Hosting [id=2, name=heroku.com]
Hosting [id=3, name=cloudbees.com]

MongoDB console.

>mongo
> db.sequence.find()
{ "_id" : "hosting", "seq" : 3 }
> db.hosting.find()
{ "_id" : NumberLong(1), "_class" : "com.mkyong.hosting.model.Hosting", "name" : "cloud.google.com" }
{ "_id" : NumberLong(2), "_class" : "com.mkyong.hosting.model.Hosting", "name" : "heroku.com" }
{ "_id" : NumberLong(3), "_class" : "com.mkyong.hosting.model.Hosting", "name" : "cloudbees.com" }
>

6. FAQs

Q. SequenceException – Unable to get sequence id for key : hosting ?
A. Remember to create the “sequence” collection!

 db.sequence.insert({_id: "hosting",seq: 0})

Download Source Code

Download – SpringData-Auto-Sequence-Example.zip (24 KB)

References

1. MongoDB – Create an Auto-Incrementing Sequence Field