Develop Reference

Connecting to an embedded OrientDB server in Java

I'm looking to run a Java process on several machines, each of which will need to start a local OrientBD server, load a graph, perform our processes, then close. As such, I need to be able to embed the OServer start process from within Java.
There is plenty of advice about how to do so, including SA questions, however most seem to be out of date (so please don't mark this as a duplicate prematurely). The most directly relevant seems to be this, however it doesn't work - at least for me. With the below code, I get the subsequent error:
try {
final OServer server = OServerMain.create();
server.startup(server.getClass().getResourceAsStream("/orientdb-server-config.xml"));
server.activate();
} catch (Exception e) {
e.printStackTrace();
System.exit(-1);
}
2021-12-07 21:47:39:323 INFO Loading configuration from input stream [OServerConfigurationLoaderXml]
2021-12-07 21:47:39:633 INFO OrientDB Server v3.2.3 (build dc98198215aa57baf29b32adb657dc3733acdb55, branch develop) is starting up... [OServer]java.lang.NullPointerException
at com.orientechnologies.orient.core.Orient.onEmbeddedFactoryInit(Orient.java:957)
at com.orientechnologies.orient.core.db.OrientDBEmbedded.<init>(OrientDBEmbedded.java:97)
at com.orientechnologies.orient.core.db.OrientDBInternal.embedded(OrientDBInternal.java:119)
at com.orientechnologies.orient.server.OServer.startupFromConfiguration(OServer.java:388)
at com.orientechnologies.orient.server.OServer.startup(OServer.java:314)
at ems.definitions.instance.Graph.<init>(Graph.java:47)
I am using OrientDB version 3.2.3; the 'ALL' .jar downloaded from here. Note that this jar does not contain the parameters file orientdb-server-config.xml, so I have downloaded it directly from the source GitHub.
Is there an issue with my specific implementation, my approach in general or with the default config file I'm using? I look forward to hearing your thoughts.

The issue was three-fold:
I was using the 'ALL' .jar provided by the website. Instead I needed to use the libraries provided in the full source.
I did not account for the fact that when the code failed, it did not delete the database it half-created, thus could not execute the code I tried to remedy. I had to implement a temporary fail-safe to drop the database prior to initialisation to avoid this.
I was using the wrong(?) strategy in general.
My working method is as below.
orientDB = new OrientDB("embedded:/tmp/","admin","adminpwd", OrientDBConfig.defaultConfig());
/** THIS IS VERY MUCH ONLY FOR LOCAL TESTING **/
if(orientDB.exists(name))
orientDB.drop(name);
if(!orientDB.exists(name)) // if the database does not already exist, create it.
orientDB.execute("create database " + name + " PLOCAL users ( admin identified by 'adminpwd' role admin)");
db = orientDB.open(name, "admin", "adminpwd");

How to do multiple add operation apache jena tdb

I have to serialize some specific properties (about ten film's properties) for a set of 1500 entity from DBpedia. So for each entity I run a sparql query in order to retrieve them and after that, for each ResultSet I store all the data in the tdb dataset using the default apache jena tdb API. I create a single statement for each property and I add them using this code:
public void addSolution(QuerySolution currSolution, String subjectURI) {
if(isWriteMode) {
Resource currResource = datasetModel.createResource(subjectURI);
Property prop = datasetModel.createProperty(currSolution.getResource("?prop").toString());
Statement stat = datasetModel.createStatement(currResource, prop, currSolution.get("?value").toString());
datasetModel.add(stat);
}
}
How can I do in order to execute multiple add operations on a single dataset? What's the strategy that I should use?
EDIT:
I'm able to execute all the code without errors, but no files were created by the TDBFactory. Why this happens?
I think that I need Joshua Taylor's help

It sounds like the query is running over the remote dbpedia endpoint. Assuming that's correct you can do a couple of things.
Firstly wrap the update in a transaction:
dataset.begin(ReadWrite.WRITE);
try {
for (QuerySolution currSolution: results) {
addSolution(...);
}
dataset.commit();
} finally {
dataset.end();
}
Secondly, you might be able to save yourself work by using CONSTRUCT to get a model back, rather than having to loop through the results. I'm not clear what's going on with subjectURI, however, but it might be as simple as:
CONSTRUCT { <subjectURI> ?prop ?value }
WHERE
... existing query body ...

I've solved my problem and I want to put here the problem that I've got for anyone will have the same.
For each transaction that you do, you need to re-obtain the dataset model and don't use the same for all the transaction.
So for each transaction that you start you need to obtain the dataset model just after the call to begin().
I hope that will be helpful.

can't insert utf-8 characters in mysql database using crontab to automate the program

I had asked the question before but because I didn't receive any guide, I'm asking it again.
Here's the original question:
fail to insert non-english characters to database using crontab to run the program
I wrote a java program that reads from a UTF-8 file and insert its contents to mysql database. I can call jar file in terminal and it works fine. after that I used crontab to automate running the program but this time only english chars and numbers will insert to DB.
My database encoding is "utf8-general-ci" and the server I'm running the program is centOs 6.3.
I should mention that I have another program that its functionality is similar to this and it works fine.
I have tested so many things but none of them fixed the problem. I don't know what's the problem.
I'm looking for a solution or any clue to continue and solve the problem. I'll appreciate any help.
EDIT:
mysql version is :5.1.69
and here is 2 images. one is for the time I run the program with crontab and the other when running the program in terminal

I'm not realy an expert on this but here goes nothing.
I think this is related to what's documented in http://dev.mysql.com/doc/refman/5.6/en/alter-table.html
Is your default character set on latin1 or something like that ? Perhaps you left it default and i think it then uses latin1.
In any case i think you have to do something like this:
ALTER TABLE target_table_name MODIFY latin1_text_col TEXT CHARACTER SET utf8;
ALTER TABLE target_table_name MODIFY latin1_varchar_col VARCHAR(M) CHARACTER SET utf8;
You can find out the default char set of the database by doing:
use db_name;
show variables like "character_set_database";
show variables like "collation_database";

I couldn't find anyway to fix the problem so I wrote a schedular program that runs the application and it works fine!!!
But I'm still confused why crontab makes that problem or what I did that program doesn't work fine!!!

Assume that you have set you db, table, and columns using utf8mb4, don't forget
specify your connection to mysql using utf8 charset:
String url = "jdbc:mysql://ip:port/db?characterEncoding=utf8";
String username = "xxx";
String password = "xxx";
try {
conn = DriverManager.getConnection(url, username, password);
} catch (SQLException e) {
e.printStackTrace();
}
--
I'm curious about the root cause of your problems as well...

Get table names from lotus notes database

I'm trying to write a program that would dump a whole lotus notes database to a file via NotesSQL driver. I'm connecting via jdbc:odbc and have
I can execute selects and get data from Lotus notes database
here is the code
try {
System.out.print("Connecting... ");
Connection con = DriverManager.getConnection("jdbc:odbc:NRC", "UserName", "Passw0rd1337");
System.out.println("OK");
DatabaseMetaData dmd = con.getMetaData();
String[] tableTypes = new String[] {"TABLE", "VIEW"};
ResultSet rs = dmd.getTables(null, null, "%", tableTypes);
ResultSetMetaData rsd = rs.getMetaData();
while (rs.next()) {
for (int i=1; i<=rsd.getColumnCount();i++)
System.out.println(i+" - "+rsd.getColumnName(i) + " - " + rs.getString(1));
}
con.close();
System.out.println("Connection closed");
} catch (Exception e) {
System.out.println(e);
}
And is there a better way to connect to Lotus notes databases via NotesSQL? Because with my code i get only null values for the names...

I know you are trying to use JDBC and NotesSQL. But, depending on your needs, and using Eclipse, you can access Notes databases natively via Java, which frankly is alot easier than trying to use JDBC, bit of a square peg in a round hole when you're using JDBC with Domino. Even if you don't have Lotus Notes installed on the host machine you can still write and deploy java applets and servlets to get into the data.
You will need to get the relevant Lotus Domino jar's though. So, my recommendation is an alternative approach to JDBC.
So, providing you have the Lotus Domino jar files in your Eclipse project you should be able to code any kind of extract from a view or even run adhoc searches on a database.
Setup
If this sounds like the direction you need to go, then firstly, have a look at setting up Eclipse with relevant Notes jar's here. There are only a few. (Sometimes you'll read about using CORBA and/or IIOP. Try avoid that, it's just a world of hurt).
Samples and snippets
This developer works article (although 6 years old) still works for Domino and is a sound foundation for the approach I am advocating. That article starts to address the initialization of the NotesFactory and Session classes to get you into the Notes API. More online help here for the NotesFactory class.
If you have a Lotus Notes client available you can have a look through code snippets here. A classic example for accessing documents via Views in Java can be found here.
After that you can easily access Views and documents with examples from here, and learn from the guru, (Bob Balaban), about memory management here.
If you're processing high volumes or running servlets, then memory management is important, otherwise don't stress about it too much. You can execute Native searches on a Notes database by writing it in formula, and then using the "search" methods to execute the query natively.
Iterating through documents or views ?
The easiest approach is to traverse documents via views and/or use "getdocumentByKey" methods to get a collection and work on that. In Domino "Views" are the equivalent of Tables. You can also get a list of Views via the Database.Views property
Native Queries
It's difficult to find definitive instructions on native queries for Notes, but I have managed to find it online here.

Postgresql 8.4 reading OID style BLOBs with Hibernate

I am getting this weird case when querying Postgres 8.4 for some records with Blobs (of type OIDs) with Hibernate. The query does return all right but when my code wants to read the content of the BLOB with the simple code below, it gets 0 bytes back
public static byte[] readBlob(Blob blob) throws Exception {
InputStream is = null;
try {
is = blob.getBinaryStream();
return org.apache.commons.io.IOUtils.toByteArray(is);
}
finally {
if (is != null)
try {
is.close();
}
catch(Exception e) {}
}
}
Funny think is that I am getting this behavior only since I've started adding more then one such records to the table.
The underlying JDBC library is type 3 (postgresq 8.4-701).
Can someone give me a hint as to how to solve this issue?
Thanks
Peter

Looks like you may have found this bug:
http://opensource.atlassian.com/projects/hibernate/browse/HHH-4876

It was a while since I have run into similar issue, and since I've refreshed my memories about this topic I am thinking of sharing the results. The problem is that Postgres (and a few versions back Oracle too) will not handle the Blob content at the record creation time in the same transaction. Funny think is that one needs to pass the content after the external file (where the content gets stored eventually) has been well created and reserved for the operation. Yes, the record gets created but the Blob is blank. To have the Blob filled out with whatever you need to put in, you need that operation in a second transaction (sort of an update record). That's a funny business (maybe a major bug), ehe