document not saving in spring jpa document manager application

Question

I am developing a document management application in spring using jpa and MySQL. The application is currently accepting a document an

Answer 1

Your JPA mappings seem good. Obviously, @Lob requires data type to be byte[] / Byte[] / or java.sql.Blob. Based on that, plus your symptoms and debugging printout it seems your code doing the correct data manipulation (JPA annotations good), but the combination of spring + MySQL isn't commiting. This suggests a minor problem with your spring transactional config OR with your MySQL data type.

1. Transactional Behaviour

The relevant code in JpaDocumentRepository.java is:

@PersistenceContext
private EntityManager em;

@Override
public void save(Document document) {
    if (document.getId() == null) {this.em.persist(document);}
    else {this.em.merge(document);}
}  

• You're not using EJBs (hence no 'automatic' container-managed transactions).
• You're using JPA within Servlets/java classes (hence you require 'manual' transaction demarcation - outside servlet container; in your code or via Spring config).
• You are injecting the entity manager via @PersistenceContext (i.e. container-managed entity manager backed by JTA, not a Entity Manager resource-local transaction, em.getTransaction())
• You have marked your 'parent' method as @Transactional (i.e. spring proprietary transcations - annotation later standardised in Java EE 7).

The annotations and code should give transactional behaviour. Do you have a Spring correctly configured for JTA transactions? (Using JtaTransactionManager, not DataSourceTransactionManager which gives JDBC driver local transactions) Spring XML should contain something very similar to:

Be suspicious of additional parameters / settings.

This is the manually coded version of what Spring must do (for understanding only - don't code this). Uses UserTransaction (JTA), not em.getTransaction() of type EntityTransaction (JDBC local):

// inject a reference to the servlet container JTA tx
@Resource UserTransaction jtaTx;

// servlet container-managed EM
@PersistenceContext private EntityManager em; 

public void save(Document document) {
    try {
        jtaTx.begin();
        try {
            if (document.getId() == null) {this.em.persist(document);}
            else {this.em.merge(document);}
            jtaTx.commit();
        } catch (Exception e) {
             jtaTx.rollback();
             // do some error reporting / throw exception ...
        }
    } catch (Exception e) {
        // system error - handle exceptions from UserTransaction methods
        // ...
    }
}

2. MySQL Data Type

As shown here (at bottom), MySql Blobs are a bit special compared to other databases. The various Blobs and their maximum storage capacities are:

TINYBLOB - 255 bytes BLOB - 65535 bytes MEDIUMBLOB - 16,777,215 bytes (2^24 - 1) LONGBLOB - 4G bytes (2^32 – 1)

If (2) turns out to be your problem:

• increase the MySQL type to MEDIUMBLOB or LONGBLOB
• investigate why you didn't see an error message (v important). Was your logging properly configured? Did you check logs?