Java DB

Simple weird type-safe DB written in Java.

Warning

I do not recommend using this DB in production app. This project was never meant for production usage and may contain security vulnerabilities.

Usage

To use this DB in another project, compile it to JAR file and add it as a local dependency to your project.
Simple example:

import java.io.File;

MyDB db = new MyDB(new File("FileName"));

db.getSchema().find(TestModel.class, model -> model.getName().equals("OldName")).forEach(value -> {
    System.out.println("ID:   " + value.getId());
    System.out.println("NAME: " + value.getName());
});

db.getSchema().update(TestModel.class, new TestModel(13456, "NewName"), testModel -> testModel.getName().equals("OldName"));

db.getSchema().find(TestModel.class, model -> model.getName().equals("NewName")).forEach(value -> {
    System.out.println("ID:   " + value.getId());
    System.out.println("NAME: " + value.getName());
});

package com.yourdomain.yourapp;

public class TestModel {
    private int id;
    private String name;

    public TestModel(int id, String name) {
        this.id = id;
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }
}

Basic rules

There is only one rule you have to follow with your models. Every model has to have empty constructor - otherwise the db will throw an UnsupportedOperationException. So make sure to always include an empty constructor like this:

package com.yourdomain.yourapp;

import io.github.mtn16.annotation.Primary;

public class MyModel {
    
    public MyModel() {}
    
}

Unique keys

The @Unique annotation simply enforces the value to be unique in all saved instances. If you try to insert a duplicate value (using insert or update), you will get an exception.

Primary keys

You can add a primary key to your class. This is required if you want to refer to the class (using relations). To add a primary key you should simply create int variable and add a @Primary annotation. You can initialize the value manually or set it to -1 which will automatically fill in the value based on auto increment function. This is recommended for most scenarios because if you try to insert a duplicate key, you will get an exception.

package com.yourdomain.yourapp;

import io.github.mtn16.annotation.Primary;

public class MyModel {
    @Primary
    private int id = -1;

    public MyModel() {}
}

Relations

Example with a post class and author class. The post has one author and every author can have infinite posts. Relations are strictly 1:N (like in SQL databases) so if you want to create M:N relation, you should create a custom class to store the relations.

package com.yourdomain.yourapp;

import io.github.mtn16.annotation.Primary;
import io.github.mtn16.annotation.Relation;

public class Post {
    @Primary
    private int id = -1;

    @Relation(
            target = Author.class,
            targetKey = "id"
    )
    private int authorId;

    public Post(int authorId) {
        this.authorId = authorId;
    }

    public Post() {}
}

package com.yourdomain.yourapp;

import io.github.mtn16.annotation.Primary;

public class Author {
    @Primary
    private int id;

    public Author() {}

    public Author(int id) {
        this.id = id;
    }
}

MyDB db = new MyDB(new File("./devdb.db"));

Author author = new Author(1);

try {
    db.getSchema().insert(new Post(1));
} catch (Exception e) {
    e.printStackTrace();
}

try {
    db.getSchema().insert(new Post(1));
} catch (Exception e) {
    e.printStackTrace();
}

db.relations().findRelated(author, Post.class).forEach(System.out::println);

Warning

You should check if the author is not null - if you deleted the author from your db, the query may return null

Development

To modify this project you simply need to clone this repository and sync Gradle.

License

This project is licensed under the MIT license.