What is JDBC? Introduction to Java Database Connectivity


JDBC (Java Database Connectivity) is the Java API that manages connecting to a database, issuing queries and instructions, and dealing with consequence units obtained from the database. Launched as a part of JDK 1.1 in 1997, JDBC was one of many earliest libraries developed for the Java language.

JDBC was initially conceived as a client-side API, enabling a Java shopper to work together with a knowledge supply. That modified with JDBC 2.0, which included an elective package deal supporting server-side JDBC connections. Each new JDBC launch since then has featured updates to each the client-side package deal (java.sql) and the server-side package deal (javax.sql). JDBC 4.3, essentially the most present model as of this writing, was launched as a part of Java SE 9 in September 2017 as JSR 221.

This text presents an outline of JDBC and JDBC drivers, adopted by a hands-on introduction to utilizing JDBC to attach a Java shopper to a light-weight relational database.

How JDBC works

As a developer, you should utilize JDBC to work together with a database from inside a Java program. JDBC acts as a bridge out of your code to the database, as proven in Determine 1.

JDBC connects Java programs to databases. IDG

Determine 1. JDBC connects Java applications to databases.

JDBC vs ODBC

Earlier than JDBC, builders used Open Database Connectivity (ODBC), a language-agnostic commonplace method to accessing a relational database administration system, or RDBMS. In some methods, JDBC takes its inspiration from ODBC. The distinction is that JDBC is Java-specific, providing a programming-level interface that handles the mechanics of Java functions speaking with a database.

JDBC’s structure

The JDBC interface consists of two layers:

  1. The JDBC API helps communication between the Java software and the JDBC supervisor.
  2. The JDBC driver helps communication between the JDBC supervisor and the database driver.

The JDBC API and JDBC driver have been refined extensively through the years, leading to a feature-rich, performant, and dependable library.

JDBC is the frequent API that your software code interacts with. Beneath that’s the JDBC-compliant driver for the database you’re utilizing.

Determine 2 illustrates the JDBC structure.

The JDBC interface consists of the JDBC API and its drivers. IDG

Determine 2. JDBC’s structure consists of the JDBC API and JDBC drivers.

JDBC drivers

As an software programmer, you don’t want to right away be involved with the implementation of the driving force you employ, as long as it’s safe and official. Nonetheless, it’s helpful to bear in mind that there are 4 JDBC driver varieties:

  1. JDBC-ODBC bridge driver: A skinny Java layer that makes use of an ODBC driver below the hood.
  2. Native API driver: Gives an interface from Java to the native database shopper.
  3. Middleware driver: A common interface (“middleware”) between Java and the RDBMS’s vendor-specific protocol.
  4. Pure Java driver: A driver that implements the vendor-specific protocol immediately in Java.

Once you begin fascinated with structure and efficiency, it will likely be useful to think about the kind of driver you’re utilizing.

Easy database connections and queries

One of many advantages of programming within the Java ecosystem is that you’ll doubtless discover a steady JDBC database connector for no matter database you select. On this tutorial, we’ll use SQLite to get to know JDBC, primarily as a result of it is really easy to make use of.

The steps for connecting to a database with JDBC are as follows:

  1. Set up or find the database you need to entry.
  2. Embrace the JDBC library.
  3. Make sure the JDBC driver you want is in your classpath.
  4. Use the JDBC library to acquire a connection to the database.
  5. Use the connection to problem SQL instructions.
  6. Shut the connection if you end up completed.

We’ll undergo these steps collectively.

Step 1. Obtain and set up SQLite

SQLite is a really compact database. It is not supposed for manufacturing use however is a superb selection for rapidly attempting issues out. SQLite makes use of a file as its useful database, with out requiring any service or daemon installations.

To get began with this demonstration, first obtain the SQLite pattern database. Unzip the .db file and reserve it someplace you will not overlook. This file incorporates each a useful file-based database and pattern schema and knowledge that we are able to use.

Step 2. Import JDBC into your Java software

We might do our coding in an IDE, however coding immediately in a textual content editor will higher reveal JDBC’s simplicity. To start, you will want to have a appropriate JDK set up on your working system.

Assuming you have got a JDK put in, we are able to begin by making a easy Java program. In your textual content editor, paste within the code proven in Itemizing 1. Name this file WhatIsJdbc.java.

Itemizing 1. A easy Java program


class WhatIsJdbc{
  public static void predominant(String args[]){
      System.out.println("Howdy InfoWorld");
  }
}

Now, compile the code by coming into the command: javac WhatIsJdbc.java. Compiling will output the WhatIsJdbc.class file. Execute this file from the command line with the decision: java WhatIsJdbc.

After getting a fundamental Java program, you possibly can embody the JDBC libraries. Paste within the code from Itemizing 2 on the head of your easy Java program.

Itemizing 2. JDBC imports


import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.ResultSet;
import java.sql.Assertion;

Every of those imports gives entry to a category that facilitates the usual Java database connection:

  • Connection represents the connection to the database.
  • DriverManager obtains the connection to the database. (Another choice is DataSource, used for connection pooling.)
  • SQLException handles SQL errors between the Java software and the database.
  • ResultSet and Assertion mannequin the information consequence units and SQL statements.

You will see every of those in motion shortly.

Step 3. Add the JDBC driver to your classpath

Subsequent, you may add the SQLite driver to your classpath. Bear in mind, a JDBC driver is a category that implements the JDBC API for a selected database.

Go to the GitHub web page for SQLite driver and obtain the newest SQLite .jar. If you’re utilizing Maven or Gradle, or one thing comparable, you possibly can add the driving force through the Maven repository. You should definitely get the newest .jar file and retailer it someplace you may bear in mind.

The following time you execute your Java program, you’ll pull in that .jar file through the classpath. There are a number of methods to set the classpath. Itemizing 3 exhibits easy methods to do it utilizing a command-line swap.

Itemizing 3. Executing the SQLite driver on the Java classpath


java.exe -classpath /path-to-driver/sqlite-jdbc-3.23.1.jar:. WhatIsJdbc

Discover that we have set the classpath to level on the driver and the native listing; this manner, Java will nonetheless discover our class file.

Step 4. Acquire a database connection

The classpath now has entry to the driving force. Subsequent, change your easy Java software file to appear to be this system in Itemizing 4.

Itemizing 4. Utilizing the JDBC Connection class to connect with SQLite


import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.ResultSet;
import java.sql.Assertion;

 String sql = "SELECT id, username FROM customers WHERE id = ?";
    Checklist customers = new ArrayList<>();
    strive (Connection con = DriverManager.getConnection(myConnectionURL);
         PreparedStatement ps = con.prepareStatement(sql)) {
        ps.setInt(1, userId);
        strive (ResultSet rs = ps.executeQuery()) {
            whereas(rs.subsequent()) {
                customers.add(new Person(rs.getInt("id"), rs.getString("identify")));
            }
        }
    } catch (SQLException e) {
        e.printStackTrace();
    }
    return customers;

class WhatIsJdbc{
  public static void predominant(String[] args) {
    String url = "jdbc:sqlite:path-to-db/chinook/chinook.db";
    strive (Connection conn = DriverManager.getConnection(url){

      System.out.println("Bought it!");

    } catch (SQLException e) {
      throw new Error("Drawback", e);
    } 
  }
}

Compile and execute this code. Assuming all goes effectively, you’re going to get an affirming message.

Now, we’re prepared for some SQL instructions.

Step 5. Question the database

With the reside connection object in hand, we are able to do one thing helpful, like querying the database. Itemizing 5 exhibits easy methods to question SQLite utilizing the JDBC Connection and Assertion objects.

Itemizing 5. Querying the database with JDBC


import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.ResultSet;
import java.sql.Assertion;


class WhatIsJdbc{
  public static void predominant(String[] args) {
    String sql = "SELECT id, username FROM customers WHERE id = ?";
    String url = "jdbc:sqlite:path-to-db-file/chinook/chinook.db";
    strive (Connection conn = DriverManager.getConnection(url);
      Assertion stmt = conn.createStatement()) {

      strive {
        ResultSet rs = stmt.executeQuery("choose * from albums";);
        whereas (rs.subsequent()) {
          String identify = rs.getString("title");
          System.out.println(identify);
        }
      } catch (SQLException e ) {
            throw new Error("Drawback", e);
      } 

    } catch (SQLException e) {
      throw new Error("Drawback", e);
    } 
  }
}

In Itemizing 5 we use our Connection object to acquire a Assertion object: conn.createStatement(). We then use this object to execute an SQL question: stmt.executeQuery(question).

The executeQuery command returns a ResultSet object, which we then use to iterate over the information with whereas (rs.subsequent()). On this instance, you must see the album titles we have queried on as output.

Discover that we additionally closed the connection, through a name to conn.shut().

PreparedStatements, batch updates, and transactions

Up to now, we have coated the fundamentals of utilizing JDBC to connect with a database and problem SQL instructions. Whereas Assertions and ResultSets work effectively for frequent eventualities, you may doubtless want extra choices for bigger or extra complicated functions. Thankfully, the JDBC library continues evolving to fulfill most database entry wants.



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