Dependency Injection, IoC (Inversion of Control)

https://github.com/jalbertomr/SimpleDependencyInjectionIoC.git

Without IoC

package com.bext;
public class IoC {

    public static void main(String[] args) {
        IoC container = new IoC(); 

        User user = container.new User(); 

        user.add( "Info to persist"); 

    }

    public class User {
        MySqlDatabase database;
 

        public User() {
            this.database = new MySqlDatabase();         

        }

        void add( String data) {
            database.persist( data);         

        }
    }

    public class MySqlDatabase {
        public void persist(String data) {
            System.out.println("MySqlDatabase persisted [" + data + "]");         

        }
    }

}

Implementing Inversion of Control (IoC) , Now instance of database can be accessed for use for tests.

package com.bext;
public class IoC {

    public static void main(String[] args) {
        IoC container = new IoC(); 

        User user = container.new User( container.new MySqlDatabase()); 

        user.add( "Info to persist"); 

    }

    public class User {
        MySqlDatabase database;

 
        public User( MySqlDatabase database) {
            this.database = database; 

        }

        void add( String data) {
            database.persist( data); 

        }
    }

    public class MySqlDatabase {
        public void persist(String data) {
            System.out.println("MySqlDatabase persisted [" + data + "]"); 

        }
    }

}

Loosely coupled Architecture to define de database to use, in this case MySqlDatabase

package com.bext;
public class IoC {

    public static void main(String[] args) {
        IoC container = new IoC(); 

        User user = container.new User( container.new MySqlDatabase()); 

        user.add( "Info to persist");    }

    public class User {
        Database database; 

        public User( Database database) {
            this.database = database;         

        }

        void add( String data) {
            database.persist( data);         

        }
    }

    interface Database {
        public void persist(String data);     

    }

    public class MySqlDatabase implements Database {
        public void persist(String data) {
            System.out.println("MySqlDatabase persisted [" + data + "]"); 

        }
    }

    public class OracleDatabase implements Database {
        public void persist(String data) {
            System.out.println("OracleDatabase persisted [" + data + "]"); 

        }
    }
}

The Run shows:

MySqlDatabase persisted [Info to persist]

The same  but now for use Oracle Database

package com.bext;
public class IoC {

    public static void main(String[] args) {
        IoC container = new IoC();         

        User user = container.new User( container.new OracleDatabase()); 

        user.add( "Info to persist"); 

    }

    public class User {
        Database database;
        public User( Database database) {
            this.database = database;        }

        void add( String data) {
            database.persist( data);        }
    }

    interface Database {
        public void persist(String data);    }

    public class MySqlDatabase implements Database {
        public void persist(String data) {
            System.out.println("MySqlDatabase persisted [" + data + "]");        }
    }

    public class OracleDatabase implements Database {
        public void persist(String data) {
            System.out.println("OracleDatabase persisted [" + data + "]");        }
    }
}

The Run shows:

OracleDatabase persisted [Info to persist]

eot