Given a sqlite database as input, I want to know how can i can generate an ORMLite java class that map with the associated database. Many thanks.
You could try Telosys Tools, an Eclipse plugin for code generation
working from an existing database with customizable Velocity templates
See: https://sites.google.com/site/telosystools/
A set of templates is available on GitHub for JPA :
//github.com/telosys-tools-community/jpa-templates-TT206-v2
A Java class for JPA is very near to ORMLite so it's possible to adapt the templates
in oder to generate ORMLite java classes
A global tutorial for Spring MVC and JPA :
//sites.google.com/site/telosystutorial/springmvc-jpa-springdatajpa
(you can just consider the JPA bundle)
I am new to ORMLite and also have the same need.
For SQLite, I read and parse the SQL statement in the field "sql" of table "sqlite_master".
Although it works well with tables, I had to find an other way to deal with views; now I use Excel to load data from views into ADO objects and parse fields' properties to generate Java POJO class definition text, then paste it onto IDE.
It's not perfect, saved me a lot of time though.
This is not something that ORMLite can do itself -- you are going to have to help it. If you want to edit your question and include your SQLite schema, I'll edit my answer to include some of the necessary object.
For example, here are some field mappings:
INTEGER -> int
VARCHAR -> String
BOOLEAN -> boolean
TIMESTAMP -> Date
BIGINT -> long
...
I would suggest creating a class and using the TableUtils.getCreateTableStatements(ConnectionSource, Class<T>) method to see what schema is dumped out and how it compares to your existing schema. Then add or modify the fields until you get as close a match as possible.
Related
I'm using the sea-orm library to manage my database. The uuid() and date_time() types are part of the sea-orm migration syntax. When sea-orm generates the entities from the SQLite database, uuid() and date_time() get converted into String.
Should I change these types on the entities manually for some other type if I want them to be type-checked? How can I do that? What types can I use? Will I have to convert them back to String when importing data into the database? How can I do that?
I have an Ionic App using SQLite. I don't have any problems with implementation.
The issue is that I need to import an SQL file using SQLitePorter to populate the database with configuration info.
But also, on the same database I have user info, so my question is:
Everytime I start the app, it will import the sql file, fill the database and probably overwrite my user data too? Since it is all on the same base?
I assume that you can always init your table using string queries inside your code. The problem is not that you are importing a .sql file. Right?
According to https://www.sqlitetutorial.net/sqlite-create-table/ it is obvious that you always create a table with [IF NOT EXISTS] switch. Writing a query like :
CREATE TABLE [IF NOT EXISTS] [schema_name].table_name (
column_1 data_type PRIMARY KEY);
you let sqlite to decide if it's going to create a table with the risk to overwrite an existing table. It is supposed that you can trust that sqlite is smart enough, not to overwrite any information especially if you use 'BEGIN TRANSACTION' - 'COMMIT' procedure.
I give my answer assuming that you have imported data and user data in distinct tables, so you can manipulate what you populate and what you don't. Is that right?
What I usually do, is to have a sql file like this:
DROP TABLE configutation_a;
DROP TABLE configutation_b;
CREATE TABLE configutation_a;
INSERT INTO configutation_a (...);
CREATE TABLE configutation_b;
INSERT INTO configutation_b (...);
CREATE TABLE IF NOT EXIST user_data (...);
This means that every time the app starts, I am updating with the configuration data I have at that time (that's is why we use http.get to get any configuration file from a remote repo in the future) and create user data only if user_data table is not there (hopefully initial start).
Conclusion: It's always a good practice, in my opinion, to trust a database product 100% and abstractly let it do any transaction that might give you some risk if you implemented your self in your code; since it gives a tool for that.For example, the keyword [if not exists], is always safer than implementing a table checker your self.
I hope that helps.
PS: In case you refer in create database procedure, SQLite, connects to a database file and it doesn't exist, it creates it. For someone comfortable in sqlite command line, when you type
sqlite3 /home/user/db/configuration.db will connect you with this db and if the file is not there, it will create it.
I have an entity that requires a GUID for it's primary key. Ideally, I would like to use a java class to generate the GUID before adding the entity to the database, so that I can control exactly how the GUID is created.
Is it possible to delegate the key generation to a java class with WSO2 DSS? How?
you can try to generate the GUID within the SQL statement, using ORACLE (for example) functions. I guess you will success if the algorithm is not too complex. This way, your insert statement would look like:
Insert into table (c1, c2, ..) values (functions for ID, v2,...)
Although the best practice is to use a trigger before insert which call a database sequence to generate a new guid.
You can also try to make a xslt transformation where you implement the algorithm to generate de guid. You would just have to perform the transformation before calling to dss.
Hope it helps!
My situation
I have a c# object which contains some lists. One of these lists are for example a list of tags, which is a list of c# "SystemTag"-objects. I want to instantiate this object the most efficient way.
In my database structure, I have the following tables:
dbObject - the table which contains some basic information about my c# object
dbTags - a list of all available tabs
dbTagConnections - a list which has 2 fields: TagID and ObjectID (to make sure an object can have several tags)
(I have several other similar types of data)
This is how I do it now...
Retrieve my object from the DB using an ID
Send the DB object to a "Object factory" pattern, which then realise we have to get the tags (and other lists). Then it sends a call to the DAL layer using the ID of our C# object
The DAL layer retrieves the data from the DB
These data are send to a "TagFactory" pattern which converts to tags
We are back to the Object Factory
This is really inefficient and we have many calls to the database. This especially gives problems as I have 4+ types of lists.
What have I tried?
I am not really good at SQL, but I've tried the following query:
SELECT * FROM dbObject p
LEFT JOIN dbTagConnection c on p.Id= c.PointId
LEFT JOIN dbTags t on c.TagId = t.dbTagId
WHERE ....
However, this retreives as many objects as there are tagconnections - so I don't see joins as a good way to do this.
Other info...
Using .NET Framework 4.0
Using LINQ to SQL (BLL and DAL layer with Factory patterns in the BLL to convert from DAL objects)
...
So - how do I solve this as efficient as possible? :-) Thanks!
At first sight I don't see your current way of work as "inefficient" (with the information provided). I would replace the code:
SELECT * FROM dbObject p
LEFT JOIN dbTagConnection c on p.Id= c.PointId
LEFT JOIN dbTags t on c.TagId = t.dbTagId
WHERE ...
by two calls to the DALs methods, first to retrieve the object main data (1) and one after that to get, only, the data of the tags related (2) so that your factory can fill-up the object's tags list:
(1)
SELECT * FROM dbObject WHERE Id=#objectId
(2)
SELECT t.* FROM dbTags t
INNER JOIN dbTag Connection c ON c.TagId = t.dbTagId
INNER JOIN dbObject p ON p.Id = c.PointId
WHERE p.Id=#objectId
If you have many objects and the amount of data is just a few (meaning that your are not going to manage big volumes) then I would look for a ORM based solution as the Entity Framework.
I (still) feel comfortable writing SQL queries in the DAOs to have under control all queries being sent to the DB server, but finally it is because in our situation is a need. I don't see any inconvenience on having to query the database to recover, first, the object data (SELECT * FROM dbObject WHERE ID=#myId) and fill the object instance, and then query again the DB to recover all satellite data that you may need (the Tags in your case).
You have be more concise about your scenario so that we can provide valuable recommendations for your particular scenario. Hope this is useful you you anyway.
We used stored procedures that returned multiple resultsets, in a similar situation in a previous project using Java/MSSQL server/Plain JDBC.
The stored procedure takes the ID corresponding to the object to be retrieved, return the row to build the primary object, followed by multiple records of each one-to-many relationship with the primary object. This allowed us to build the object in its entirety in a single database interaction.
Have you thought about using the entity framework? You would then interact with your database in the same way as you would interact with any other type of class in your application.
It's really simple to set up and you would create the relationships between your database tables in the entity designer - this will give you all the foreign keys you need to call related objects. If you have all your keys set up in the database then the entity designer will use these instead - creating all the objects is as simple as selecting 'Create model from database' and when you make changes to your database you simply right-click in your designer and choose 'update model from database'
The framework takes care of all the SQL for you - so you don't need to worry about that; in most cases..
A great starting place to get up and running with this would be here, and here
Once you have it all set up you can use LINQ to easily query the database.
You will find this a lot more efficient than going down the table adapter route (assuming that's what you're doing at the moment?)
Sorry if i missed something and you're already using this.. :)
As far I guess, your database exists already and you are familiar enough with SQL.
You might want to use a Micro ORM, like petapoco.
To use it, you have to write classes that matches the tables you have in the database (there are T4 generator to do this automatically with Visual Studio 2010), then you can write wrappers to create richer business objects (you can use the ValueInjecter to do it, it is the simpler I ever used), or you can use them as they are.
Petapoco handles insert / update operations, and it retrieves generated IDs automatically.
Because Petapoco handles multiple relationships too, it seems to fit your requirements.
Can someone help me answer these questions on EntityFramework?
Does it do anything special to the database? (like extra tables)
Can I add data directly with SQL without breaking EF?
Can I add tables and fields without breaking EF?
Yes you can access database with plain SQL when using EF.
No. EF just uses database. There is one exception in code first approach where EF can create one additional table for its own purpose called EdmMetadata.
Yes you can add data directly with SQL. If both your entity model and database are defined correctly it will not break EF.
Yes you can add new tables directly but EF will not know about them. You should not change existing tables because it can break EF.
You can do it with:
var context = new YourObjectContext();
var s = context.ExecuteStoreCommand("some query");
if your query create a table, this only create a table on db and not effected on EF