In Process Mode of HSQLDB in web application.


If you want to use the database into your web application, you can use the HSQLDB in In_Process mode. In this mode, you can embed the HSQLDB into your web application and it runs as a part of your web application programm in the same JVM. In this mode, the database does not open any port to connect to the application on the hosing machine and you don't need to configure anything to access it. Database is not expposed to other application and can not be accessed from any dabase tools like dbVisualizer etc. In this mode ,database will be unknown from any other person except you.

But in the 1.8.0 version, you can use Server intance for external as well as in process access.  To close the databse, you can issue SHUTDOWN command as an SQL query.

  In the in-process mode, database starts from JDBC with the associated databse file provided through  connection URL. for example

  DriverManager.getConnection("jdbc:hsqldb:mydatabase","SA","");

  Here mydatabase is the database file being used to hold the data tables. you can use relative path also along with file name.
 
To embed the Hsqldb in your web application, you require only hsqldb.jar file in class path. This library contains all required classes. See the following web application that uses Hsqldb in embedded mode.
Download Source Code
UsingHdqlDb
│   index.html
│   
└───WEB-INF
    │   web.xml
    │
    └───classes
    │       Register.class
    │       Register.java
    │       ViewRecords.class
    │       ViewRecords.java 
    └───lib
            hsqldb.jar
 

Index.html
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>
  <head>
    <title>Register Here</title>
  </head>
  <body>
   <form method = "post" action = "Register">
    User Name<br/>
    <input type = "text" name = "name"/>
    <br/>
    Email<br/>
    <input type = "text" name = "email"/>
    <br/>
    Phone no<br/>
    <input type = "text" name = "phone"/>
    <br/>
    <input type = "submit" values = "Submit"/>
    </form>
  </body>
</html>


web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app>
    <servlet>
    <description></description>
    <display-name>Register</display-name>
    <servlet-name>Register</servlet-name>
    <servlet-class>Register</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Register</servlet-name>
    <url-pattern>/Register</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>ViewRecords</display-name>
    <servlet-name>ViewRecords</servlet-name>
    <servlet-class>ViewRecords</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ViewRecords</servlet-name>
    <url-pattern>/ViewRecords</url-pattern>
  </servlet-mapping>
</web-app>


Register.java
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Register extends HttpServlet {
    Connection con;
    @Override
    public void init() throws ServletException {
        try {
            Class.forName("org.hsqldb.jdbc.JDBCDriver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace(System.out);
        }
        try {
            con=DriverManager.getConnection("jdbc:hsqldb:mydatabase","SA","");
            con.createStatement().executeUpdate("create table contacts (name varchar(45),email varchar(45),phone varchar(45))");
        } catch (SQLException e) {
            e.printStackTrace(System.out);
        }
    }
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter out=response.getWriter();
        String name=request.getParameter("name");
        String email=request.getParameter("email");
        String phone=request.getParameter("phone");
        try {
            PreparedStatement pst=con.prepareStatement("insert into contacts values(?,?,?)");
            pst.clearParameters();
            pst.setString(1, name);
            pst.setString(2, email);
            pst.setString(3, phone);
            int i=pst.executeUpdate();
            out.write(i+" records inserted, <a href='ViewRecords'>View Records</a>");
        } catch (SQLException e) {
            e.printStackTrace(System.out);
        }
    }
}


ViewRecords.java
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ViewRecords extends HttpServlet {
    Connection con;
    @Override
    public void init() throws ServletException {
        try {
            Class.forName("org.hsqldb.jdbc.JDBCDriver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace(System.out);
        }
        try {
            con=DriverManager.getConnection("jdbc:hsqldb:mydatabase","SA","");
        } catch (SQLException e) {
            e.printStackTrace(System.out);
        }
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter out=response.getWriter();
        try {
            PreparedStatement pst=con.prepareStatement("select * from contacts");
            pst.clearParameters();
            ResultSet rs=pst.executeQuery();
            while(rs.next()){
                out.write("<br/>"+rs.getString(1));
                out.write(", "+rs.getString(2));
                out.write(", "+rs.getString(3));
            }
            out.write("<hr/><a href='index.html'>Home</a> ");
        } catch (SQLException e) {
            e.printStackTrace(System.out);
        }
    }

}


See also :

HSQLDB - Handling Database Programatically (In-Process and Server Mode at a time )

http://www.programmingforfuture.com/2010/06/using-hypersql-hsqldb.html

6 comments:

Anonymous said...

Looks great ! Big thanks !

John Goyer said...

I like the bare-bones approach here. Very easy to see what is going on. Thanks.

SingleInCharlotte said...

I tried changing your code around and I can not get it to work I am using netbeans for an IDE I keeping getting a java.lang.NullPointerException error. Can I post the code some place for someone to look at

Hemraj said...

Have you included file "hsqldb.jar" in classpath?

Jefer Song said...

Hi first many thanks for the tutorial helped me a lot in building a swing app with an embedded db, however I'm not able to locate where is saving the data, could you explain me please, many tks in advance

Anonymous said...

Thanks for a great post. I was up and running in only a few minutes.

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