Getting an exception when trying to persist Pattern object from java.util.regex package ( using Berk

Neelkamal-Oracle

Hello,

we are evaluating berkeley DB Java to replace our file based storage and have the following questions

1. Does berkeley db support Pattern class from java.util.regex package ?
   We  have a persistent class with Pattern object which when being loaded into the entity store is resulting in the below exception
   Exception: java.lang.IllegalArgumentException: Class could not be loaded or is not persistent: java.util.regex.Pattern
2. Is there a way to avoid the default constructor requirement in each Persistent class?
3. Are there any restrictions on the type of java classes supported by BK DB?

can someone help me with above questions ?

Thanks,

Neel

Greybird-Oracle

Hi Neel,

With the DPL you can persist classes that are not annotated with @Persistent (or @Entity), but you need to use a PersistentProxy -- see the javadoc for this interface.

--mark

Greybird-Oracle

Hi Neel,

With the DPL you can persist classes that are not annotated with @Persistent (or @Entity), but you need to use a PersistentProxy -- see the javadoc for this interface.

--mark

Neelkamal-Oracle

Thanks mark…that’s what I was looking for. I was able to implement a proxy class for java.util.regex.Pattern but when I try to do the same for java.sql.Timestamp I am running into this error

Cannot embed a reference to a proxied object in the proxy

Any thoughts ?

Greybird-Oracle

There must be a mistake in your proxy, perhaps a Pattern in the Timestamp proxy, or vice-versa?  Please post the stack trace and the code for both proxies.

Neelkamal-Oracle

Both of them are independent. Pattern works but Timestamp ( tried with both java.sql.Timestamp and com.sleepycat.je.utilint.Timestamp ) is giving me the error

Proxy class for Pattern :

@Persistent(proxyFor = Pattern.class)
public class PersistentProxyForPattern implements PersistentProxy<Pattern> {
  Pattern pattern;
  @Override
  public Pattern convertProxy() {
  return pattern;
  }
  @Override
  public void initializeProxy(Pattern arg0) {
  pattern = arg0;
  }
}

Proxy class for Timestamp :

@Persistent(proxyFor = Timestamp.class)
public class BK_ProxyForTimestamp implements PersistentProxy<Timestamp> {
  Timestamp tstamp;
  @Override
  public Timestamp convertProxy() {
  return tstamp;
  }
  @Override
  public void initializeProxy(Timestamp arg0) {
  tstamp = arg0;
  }
}

Timestamp Proxy class registration

 EntityModel model = new AnnotationModel();
  model.registerClass(BK_ProxyForTimestamp.class);
  storeConfig.setModel(model); 
  store = new EntityStore(envmnt, "EntityStore", storeConfig);

This is the exact message I am seeing in the console. No additional stack trace

Cannot embed a reference to a proxied object in the proxy; for example, a collection may not be an element of the collection because collections are proxied

Greybird-Oracle

You should be getting an error for both of these. The fields of the proxy (which are stored by the DPL) must be non-proxied objects. So for a Pattern proxy, you probably want to store it as a String field, and for a Timestamp proxy you could probably use a 'long' field.

--mark

Neelkamal-Oracle

Thanks Mark I am all set for now.

But l still don't see any error when i use pattern object in the Pattern proxy class. I get a Null Pointer Exception when i try to retrieve the data though.

I am attaching a sample code for your reference

myEntity

@Entity
public class myEntity {
  @PrimaryKey
  private String Id;
  Pattern regex;
  public Pattern getRegex() {
  return regex;
  }
  public void setRegex(Pattern regex) {
  this.regex = regex;
  }
  public String getId() {
  return Id;
  }
  public void setId(String id) {
  Id = id;
  }
}

myDA

public class myDA {
  PrimaryIndex<String, myEntity> pIdx;
  public myDA(EntityStore store) throws DatabaseException {
  pIdx = store.getPrimaryIndex(String.class, myEntity.class);
  } }

ProxyForPattern

@Persistent(proxyFor = Pattern.class)
public class PersistentProxyForPattern implements PersistentProxy<Pattern> {
  Pattern pattern;
  @Override
  public Pattern convertProxy() {
  return pattern;
  }
  @Override
  public void initializeProxy(Pattern arg0) {
  pattern = arg0;
  }
}

myDriver

public class myDriver {
  private static File envHome = new File("dbEnv");
  private Environment envmnt;
  private EntityStore store;
  private myDA sda;

  public void setup() throws DatabaseException {
  EnvironmentConfig envConfig = new EnvironmentConfig();
  StoreConfig storeConfig = new StoreConfig();
  envConfig.setAllowCreate(true);
  envConfig.setTransactional(true);
  storeConfig.setAllowCreate(true);
  storeConfig.setTransactional(true);
  envmnt = new Environment(envHome, envConfig);
  EntityModel model = new AnnotationModel();
  model.registerClass(PersistentProxyForPattern.class);
  storeConfig.setModel(model);
  store = new EntityStore(envmnt, "EntityStore", storeConfig);
  }

  public void shutdown() throws DatabaseException {
  store.close();
  envmnt.close();
  }

  private void putData() throws DatabaseException {
  setup();
  sda = new myDA(store);
  myEntity sec1 = new myEntity();
  Pattern regex = Pattern.compile("a*b");
  sec1.setId("id1");
  sec1.setRegex(regex);
  Transaction txn = envmnt.beginTransaction(null, null);
  try {
  sda.pIdx.put(txn, sec1);
  txn.commit();
  } catch (Exception e) {
  if (txn != null) {
  txn.abort();
  txn = null;
  }
  }
  shutdown();
  }

  private void getData() throws DatabaseException {
  setup();
  sda = new myDA(store);
  myEntity sec1 = sda.pIdx.get("id1");
  System.out.println("sec1 details" + " " + sec1.getId() + " " + sec1.getRegex());
  shutdown();
  }

  public static void main(String[] args) {
  myDriver ssp = new myDriver();
  try {
  System.out.println("Inserting data");
  ssp.putData();
  System.out.println("Inserting data");
  ssp.getData();
  } catch (DatabaseException dbe) {
  System.err.println("SimpleStorePut: " + dbe.toString());
  dbe.printStackTrace();
  } catch (Exception e) {
  System.out.println("Exception: " + e.toString());
  e.printStackTrace();
  }
  }
}