Fortunatly we have evolution in play framework 2 so we don't care about schema (if we want). My question is, is there any practice with loading data to the database on application startup? I suppose that I can load it with Global object, but what the approach needs less code and more flexible(in java)?
Take a look on the same question (and answer), the official way is showed in Zentasks sample.
you can also use common evolutions to insert data in raw SQL format (it doesn't work only with schema)
Related
Note:There is a good chance I'm not using the correct terminology here and that maybe the reason I'm not finding the answers to my question. I apologize upfront if this has been already answered, so please just direct me there.
I am looking for an open source framework written in Java that would allow me to build pluggable data connectors (and obviously have some built in already) and almost have a query language (abstraction layer) that would translate into any of those connections.
For example: I would be able to say:
Fetch 1 record from a Mongo DB that matches name='John Doe'
and get JSON as a response
or I could say
Fetch all records from a MySQL DB that matches name='John Doe'
and get a JSON as a response
If not exactly what I described, I am willing to work with anything that would have a part of this solved.
Thank you in advance!
You're not going to find a "Swiss army knife" data abstraction framework that does all of the above. Perhaps the closest things to what you ask for would be JPA providers for both Mongo and MySQL (Hibernate is a well-regarded JPA provider for MySQL, and a quick google search shows Kundera, DataNucleus and Hibernate OGM for Mongo). This will let you map your data to Java Objects, which might be a step further than what you ask for since you explicitly asked for JSON; however, there are numerous options for mapping the resulting objects into JSON if you need to present JSON to a user or another system (Jackson comes to mind for this).
Try YADA, an open source data-abstraction framework.
From the README:
YADA is like a Universal Remote Control for data.
For example, what if you could access
any data set
at any data source
in any format
from any environment
using just a URL
with just one-time configuration?
You can with YADA.
Or, what if you could get data
from multiple sources
in different formats
merging the results
into a single set
on-the-fly
with uniform column names
using just one URL?
You can with YADA.
Full disclosure: I am the creator of YADA.
Unfortunately I couldn't find anything specific to this topic / to my problem. Here we go:
I'm building a JavaFX Business Application for a friend of mine. Unfortunately I do not have any possibility to connect to a Database. I want the Application to load a savestate from a file. The application contains a list with clients and the clients got some specific properties. I do not want to hardcode this to a .prop or .txt file, because I'm sure that there's a different way of doing this, isn't there?
Thanks in advance, appreciate it!
Lots of choices for persisting data to local storage. The exact choice depends on your needs. You do not describe enough details to make a specific recommendation.
Here is a list of possibilities, roughly in increasing order of complexity of your data.
Text file
If you have small amounts of simple data, save to a text file. You can store each piece in a separate file, or combine into a single file. Recent versions of Java have new classes to make this easier than ever. See Oracle Tutorial.
Comma-separate & Tab-delimited
For sets of structured data, write to text files in comma-separated values (CSV) or tab-delimited values. For example a list of people with rows for each person, and columns for name, phone number, and email address.
While reading/writing such files is easy enough to program yourself, I suggest using an established library to eliminate the drudgery, avoid bugs, and save yourself some time. There are a few such libraries written in Java.
My favorite is the Apache Commons CSV project. This library makes easy work of the chore of reading/writing such files. Despite the name, this library supports tab-delimited as well as comma-separated formats. I've written a few Answers here on Stack Overflow showing how to use this library, as you can see here, here, and here.
By the way, plain old ASCII defines a few character positions explicitly for delimiting in data files, with four levels of grouping (document, group, record/row, and field). Unicode, of course, inherits these from ASCII as code points. I am puzzled why these have remained so obscure and so infrequently used. Seems much more logical to me than using commas and tabs which may well exist inside the data payload.
Serialization
You can write out the data values stored within an object. This is called serialization. Java has a serialization facility built-in, but be sure to study up on the details.
To more simply write out an object’s values and later read them back in to reconstitute an object, I have enjoyed using the Simple XML Serialization project. This works well for relatively simple needs, and is aimed at the situation where you want the structure of a class to drive the process of determining what to write.
Java has other XML binding facilities both built-in and third-party. These are much more powerful in their flexibility. They are especially good for when you want to define and verify the XML structure in a rigid fashion such as defining a XML DTD or XML Schema against which to validate the data and perhaps even generate the Java class in which to represent the data.
Embedded database
For more complicated data, use an embedded relational database.
The SQLite database is bundled with many platforms. This is a C-based library, not pure Java. As the name indicates, SQLite is indeed quite “lite“, lacking rigid data types and many other common database features. SQLite is meant to be an alternative to writing text files than as a competitor to more serious databases. It is a great product if your needs fit the sweet-spot of its capabilities.
My first choice for an embedded database would be H2 Database Engine. Built in pure Java. Can be run inside your app, or separately as a server (you choice). Has sophisticated relational database features. Has been around for years, often updated, and is well-worn. The principal author has much experience in the field.
Summary:
I am trying to write a utility program that is based on the information contained in a separate file. The object has to be such that any information on the physical file can be retrieved quickly and can be updated quickly as well.
Details:
The file is a normal ANSI encoded file that is supposed to store definitions of the physical quantities stated in the SI system. What I really want is that I should be able to read and write changes to the definitions whenever required. I'll be using markers(like ":") to get the headings and definitions like:
Length:metre:m:"..length of path traveled by light in vacuum in
1/299792458th of a second"
and so on.
So in this case is extending RandomAccessFile an option? Will it help me in quick retrieval and syncing of data? Should I use another approach?
If you want these things, then I'd advise you to use an embedded ACID database like H2:
Guarantee that you don't lose changes that you made
Have more than one program access the info
This is because coding up something that correctly does this using low level facilities like RandomAccessFile is quite hard. Storing persistent application state in embedded DBs is commonly done. H2 is probably the most popular among DBs implemented in pure Java.
On how to actually do this, see this: Embedding the Java h2 database programmatically
You prob. want to look at introduction on relational DBs & SQL if you aren't familiar with them.
I'd like to save persistent objects to the file system using Hibernate without the need for a SQL database.
Is this possible?
Hibernate works on top of JDBC, so all you need is a JDBC driver and a matching Hibernate dialect.
However, JDBC is basically an abstraction of SQL, so whatever you use is going to look, walk and quack like an SQL database - you might as well use one and spare yourself a lot of headaches. Besides, any such solution is going to be comparable in size and complexity to lighweight Java DBs like Derby.
Of course if you don't insist absolutely on using Hibernate, there are many other options.
It appears that it might technically be possible if you use a JDBC plaintext driver; however I haven't seen any opensource ones which provide write access; the one I found on sourceforge is read-only.
You already have an entity model, I suppose you do not want to lose this nor the relationships contained within it. An entity model is directed to be translated to a relational database.
Hibernate and any other JPA provider (EclipseLink) translate this entity model to SQL. They use a JDBC driver to provide a connection to an SQL database. This, you need to keep as well.
The correct question to ask is: does anybody know an embedded Java SQL database, one that you can start from within Java? There are plenty of those, mentioned in this topic:
HyperSQL: stores the result in an SQL clear-text file, readily imported into any other database
H2: uses binary files, low JAR file size
Derby: uses binary files
Ashpool: stores data in an XML-structured file
I have used HyperSQL on one project for small data, and Apache Derby for a project with huge databases (2Gb and more). Apache Derby performs better on these huge databases.
I don't know exactaly your need, but maybe it's one of below:
1 - If your need is just run away from SQL, you can use a NoSQL database.
Hibernate suports it through Hibernate OGM ( http://www.hibernate.org/subprojects/ogm ).
There are some DBs like Cassandra, MongoDB, CouchDB, Hadoop... You have some suggestions Here
.
2 - Now, if you want not to use a database server (with a service process running always), you can use Apache Derby. It's a DB just like any other SQL, but no need of a server. It uses a singular file to keep data. You can easily transport all database with your program.
Take a look: http://db.apache.org/derby/
3 - If you really want some text plain file, you can do like Michael Borgwardt said. But I don't know if Hibernate would be a good idea in this case.
Both H2 and HyperSQL support embedded mode (running inside your JVM instead of in a separate server) and saving to local file(s); these are still SQL databases, but with Hibernate there's not many other options.
Well, since the question is still opened and the OP said he's opened to new approaches/suggestions, here's mine (a little late but ok).
Do you know Prevayler? It's a Java Prevalence implementation which keep all of your business objects in RAM and mantain Snapshots/Changelogs in the File System, this way it's extremely fast and reliable, since if there's any crash, it'll restore it's last state and reapply every change to it.
Also, it's really easy to setup and run in your app.
Ofcourse this is possible, You can simply use file io features of Java, following steps are required:-
Create a File Object
2.Create an object of FileInputStream (though there are ways which use other Classes)
Wrap this object in a Buffer object or simply inside a java.util.Scanner.
use specific write functions of the object created in previous step.
Note that your object must implement Serializable interface. See following link,
We have an application (Java) with an own OR mapper. Within this system we have what can be compared to Hibernate's interceptors (we call it triggers): Do specific actions just before saving data in the database, after it's deleted and so on. The underlying database is MySQL.
Now we would like to use tools such as Pentaho Data Integration or Talend to convert data to put it into our system. It's no problem to do that directly on the SQL level, but by doing so we loose the built-in power of our triggers.
Is there a way to somehow integrate any of the Data Integration solutions into our existing application? It would be great if there was a way to write into instances of our classes instead of writing into the database directly.
Any hints welcome :-)
I'd prefer Talend which is a Java code generator tool. (You can se my blog post at http://www.robertomarchetto.com/www/talend_studio_vs_kettle_pentao_pdi_comparison)
You could use a tJavaRow so you can write Java code for each processed row. In tJavaRow you can call Hibernate code, for example using a custom class defined in a new routine.
2 ways with Pentaho data integration I can think of straight off:
Simply create a plugin which adds/deletes data - you could copy the existing salesforce insert/update plugins, they would be a good start - rip out all the salesforce code and replace with yours.
Perhaps harder; But maybe more satisfying - Write a jdbc driver which uses your code!