Barcode Servlet Implementation

Barcode for Java's Java Servlets may be used to add server-side barcode generation capability to a dedicated web server. Barcode for Java's Servlet is compatible with all browsers and is easy to embed in HTML as an image with the <IMG> tag.

Servlet Implementation:

Example Using JSDK:

  1. Place the barcode JAR or class files in the CLASSPATH. In Windows®, this is accomplished by modifying the CLASSPATH environment variable to include the full path to the JAR file. As an example, the following will add LinearBarCode.jar to the classpath:
    SET CLASSPATH=.;c:\java\classroot\;c:\jars\linear.jar
  2. Install JDK 1.2 or above or verify that JDK 1.2 or above is installed on the server. The encoder requires Java 2 or JDK 1.2 or above to create the JPEG files used by the servlet.
    Special requirements for Linux and Unix servers:

    1. Be sure Java.awt GUI functions are available in the environment. If the Java environment has the java.awt library stripped out, then the encoder will be unable to create image files.
    2. If the UNIX or Linux server does not have an X-Window environment, then either (1) use Headless Java or (2) connect to a remote X Server or (3) install the X Windows environment and run an X Windows session or (4) install an emulator, PJA library or virtual frame buffer.
  3. Install the appropriate servlet server code on the server and make sure it is specified in the CLASSPATH. For example:
    SET CLASSPATH=.;c:\java\classroot\;c:\jars\linear.jar;c:\jsdk2.1\server.jar;c:\jsdk2.1\servlet.jar
  4. Per the JSDK instructions, edit c:\jsdk2.1\examples\WEB-INF\servlets.properties to include the following statement:
    LinearServlet.code=com.businessrefinery.barcode.linear.LinearServlet
  5. Next, start the servlet server by executing C:\jsdk2.1\startserver.bat.
  6. After the servlet server is started, type the following code into the browser and specify applet parameters to create the barcode. This URL creates the a barcode encoding "123456789" with a height if .8cm:
    http://localhost:8080/examples/servlet/LinearServlet?BARCODE=123456789&BAR_HEIGHT=.8

Servlet Implementation Using ServletExec ISAPI on Windows® Server:

  1. In the servlet administration area choose Configure.
  2. Choose Add Servlet and enter the servlet name, class and code base.
  3. Choose Submit and choose to Reload the new servlet.
  4. The servlet should now be viewable online by entering a URL such as
    http://yourserver.com/servlet/LinearServlet?BARCODE=123456789

Inserting barcodes into HTML - after the servlet is working:

  1. Barcodes may be integrated within web pages and HTML forms by using an IMG tag, for example:
    <img src="http://barcodeforjava.ws/servlet/LinearServlet?HEIGHT=80&WIDTH=170&BARCODE=123456780&BAR_HEIGHT=.8">
    Notice in the above code that the HEIGHT and BAR_HEIGHT are different. The HEIGHT and WIDTH parameter should be set to the maximum allowed barcode size within a form.
  2. The image that is created defaults to the screen resolution of 96 DPI and may be compressed if necessary to obtain smaller X dimensions or precision. Because of the screen’s resolution, the X dimension can only be adjusted within increments of .03cm. For example, if an X dimension of .015 is needed, the image on the web page must be compressed by 50%. The following HTML tag reduces the image by 50%; it will not look correct on the screen but it will print correctly.
    <IMG height=40 alt="Barcode Image" src="http://barcodeforjava.com/servlet/lin?HEIGHT=80&WIDTH=160&BARCODE=123456789" width=80>

Creating secure servlets:

Other methods of servlet operation can be accomplished by developers that modify the servlet source code provided. This may be necessary to make sure the end-user cannot manipulate the servlet.

Auto-sizing and performance considerations:

When using the Servlet, auto sizing of the image is disabled if the HEIGHT and WIDTH are manually specified. Because a temp image is created to determine the size, performance is improved by specifying the size.