For a university assignment I have been assigned I have a Prize object which contains either text, image, or video content. I would like to persist this information into a BLOB field within an Apache Derby database (which will be running on a low powered PDA). How can I add this data to the database?
Thanks in advance.
In this article Five Steps to Managing Unstructured Data with Derby
you can read how to do this.
It describes how to insert binary data into a column with the BLOB datatype in Apache Derby using JDBC.
I assume you'll be connecting via JDBC. If so, simply write your SQL and look at the setBlob method of a PreparedStatement. Should be pretty straightforward.
Serialization is the easy way to do it, however if possible you could make it look like a real database table with a structure containing id (bigint), datatype (smallint), creationdate (date) and data (blob) and specifically make the client code to save the object's data there. This way you could do searches like "get all video prizes created between January 1st 2008 and January 15th 2009" and it wouldn't break down old data if your class would change too much for the serialization to stop working.
This sort of solution would be easy to extend in the future too if there would be need for it; I understand this is a school assignment and such need most likely won't ever surface but if your teacher/professor knows his stuff, I bet he's willing to give an extra point or two for doing this excercise in this way since it takes a bit more time and shows that you can take the steps to prepare in advance for coping in the everchanging landscape of software development.
If you are using Netbeans (I assume Eclipse has similar functionality) you can setup your database schema and the create new Java entity classes from the database and it will generate the appropriate JPA classes for you.
http://hendrosteven.wordpress.com/2008/03/06/simple-jpa-application-with-netbeans/
This is nice as it allows you to focus on your code rather than the database glue code.
The best solution , is to use Derby, because it keep being a multi platform app developed via Java.
Related
I want to store a little bit of data on my server that can be accessed easily by anyone. It's for a game I am making and I want to store a few things such as:
Game version (String)
Description (Long String)
News (Array of Strings)
Changelog (Array of Strings)
etc...
I figured that making a whole database and table for this would be overkill. I would like to be able to access the information using various types of media but I at least ant it to work with PHP (web) and Java (Desktop and android). Also the data will be updated and inputted manually by only me but readable publicly so that other websites can use it if they choose. What would I use for this kind of thing?
Extra: I might eventually want to input data manually. Things such as "Players Joined" would be managed by my server and would increment it automatically.So if it can do that too that would be great.
I have decided to use a Database and access the data with MySQL. I already have one for my game so it is a good choice because of that (this means I won't be creating a whole database just for this). I will create a table that will store this data and the table will only have 1 row (ID = 0). I will access it by selecting the row with ID = 0. I will have to create other tables with news and changelogs too.
If you have a similar question to mine, check this out:
http://www.dummies.com/how-to/content/storing-data-with-php-flat-file-or-database.html
It provided some useful advice. Also look into JSON or XML and SQLite.
You might want to check out H2 database. It can run as an embedded database (just include a jar, no extra installation, etc.), is very solid and you can get up and running very quickly.
I have a use case where in I need to read rows from a file, transform them using an engine and then write the output to a database (that can be configured).
While I could write a query builder of my own, I was interested in knowing if there's already an available solution (library).
I searched online and could find jOOQ library but it looks like it is type-safe and has a code-gen tool so is probably suited for static database schema's. In the use case that I have db's can be configured dynamically and the meta-data is programatically read and made available for write-purposes (so a list of tables would be made available, user can select the columns to write and the insert script for these column needs to be dynamically created).
Is there any library that could help me with the use case?
If I understand correctly you need to query the database structure, display the result to via a GUI and have the user map data from a file to that structure?
Assuming this is the case, you're not looking for a 'library', you're looking for an ETL tool.
Alternatively, if you're set on writing something yourself, the (very) basic way to do this is:
the structure of a database using Connection.getMetaData(). The exact usage can vary between drivers so you'll need to create an abstraction layer that meets your needs - I'd assume you're just interested in the table structure here.
the format of the file needs to be mapped to a similar structure to the tables.
provide a GUI that allows the user to connect elements from the file to columns in the table including any type mapping that is needed.
create a parametrized insert statement based on file element to column mapping - this is just a simple bit of string concatenation.
loop throw the rows in the file performing a batch insert for each.
My advice, get an ETL tool, this sounds like a simple problem, but it's full of idiosyncrasies - getting even an 80% solution will be tough and time consuming.
jOOQ (the library you referenced in your question) can be used without code generation as indicated in the jOOQ manual:
http://www.jooq.org/doc/latest/manual/getting-started/use-cases/jooq-as-a-standalone-sql-builder
http://www.jooq.org/doc/latest/manual/sql-building/plain-sql
When searching through the user group, you'll find other users leveraging jOOQ in the way you intend
The setps you need to do is:
read the rows
build each row into an object
transform the above object to target object
insert the target object into the db
Among the above 4 steps, the only thing you need to do is step 3.
And for the above purpose, you can use Transmorph, EZMorph, Commons-BeanUtils, Dozer, etc.
I want to build a fairly simple Android application.
The basic data model of my app consist on several basic elements with relationships between them.
I want the data to be persistant so I'm thinking about using an sqlite DB.
I looked at the Android Developer website, and the closest thing that I could find that is relevant to my question is the "NotePad Tutorial" which make use of an sqlite DB to store notes.
I think by now I got the handle on the basics, but I still have some questions though:
In the tutorial they have only one table in the DB. If my application requires a more complicated scheme - should I still use the same method? that is - putting everything inside a subclass of SQLiteOpenHelper? Or is there a more "structured" way to go?
Should I bother creating classes for all the data elements stored in my DB? I mean this is what I learned that I should do, but in the documentation there is no hint about that.
If I Should create classes - How should I use them correctly? I mean, since the result of the query is a Cursor object, and not a collection of rows, Should/Can I parse that into objects?
Thanks!
Define all the tables in the same subclass, this makes easy to see all the table at one place and possibly write SQL for upgade etc
Yes, that would be easier for manipulation in the java side and makes code clean
Read from the cursor and initialize an arraylist of objects one by one.
I am trying to create an application in java which pulls out records from the database and maps it to objects. It does that without knowing what the schema of the database looks like. All i want to do is fetch all rows from all tables and store them somewhere. There could be a thousand tables with thousands of records each. The application doesn't know the name of any table or attribute. It should map "on the fly". I looked at hibernate but it doesnt give me what i want for this app. I don't want to create hard-coded xml files and classes for mapping. Any ideas how i can accomplish this ?
Thanks
Oracle has a bunch of data dictionary views for metadata.
ALL_TABLES, ALL_TAB_COLUMNS would be first places to start. Then you'd build ad-hoc queries based on what you get out of there. Not sure whether you have to deal with all data types (dates, blobs, spatial, user-defined....).
Not sure what you mean by "store them somewhere". If you start thinking CSV or XML files, you'll need to escape various characters from VARCHAR2 columns.
If you are looking for some generic extract/unload routines, you should look at what is already available in the database or open-source/commercially.
MyBatis provides a pretty simple way to map data results to objects and back, maybe check that out?
http://code.google.com/p/mybatis/
Not to be flip, but for this task, you might want to check out Ruby on Rails and its ActiveRecord approach
I have a classifieds website which uses SOLR to search for whatever ads the user wants to search for... SOLR then returns the ID:s of all the matches found. I then use the ID:s to fetch and display the ads from a MySQL table.
currently I have one huge table containing everything in MySQL.
Sometimes some of the fields are empty because for instance an apartment has no "model" but a car does.
Is this a problem for me if I use SOLR like I do?
Thanks
Ask yourself these questions:
Is your current implementation slow or prone to error?
Are you adding a lot of "hacks" in order to display content or fetch data correctly due to the de-normalization of your database?
In the long run, will you benefit from normalizing the table?
Hope that helps. It all depends on your situation! Personally, I build databases normalized and then de-normalize as needed to keep things speedy.
If you are using SOLR, why don't you just serve complete ad from solr instead of MySQL to save DB time?
One huge table usually is not goog option at all.