Java Servlets (Developer Ref)

To embed a Corda image in a Java Servlet, use the Java Corda Embedder.

Embedding a Corda image into a Java Servlet can be broken down into the following steps:

Importing the Library
Instantiating a Corda Embedder Object
Setting the Server Information
Specifying Image Information
Writing the Image to a Web Page
Compiling a Servlet

The example code at the end of this section shows how to embed a Corda image in a Java Servlet.

Note: This documentation assumes that you are familiar with Java Servlets.

Importing the Library

Before importing the Corda Embedder library into a Java Servlet, first make sure that product_root\Server\dev_tools\embedder\java\CordaEmbedder.jar is in the Web Application's classpath. For more information, see Java Application Servers.

To import the Corda Embedder library, include the following line at the beginning of the Servlet.

import com.corda.CordaEmbedder;

This instructs the Servlet to import the CordaEmbedder class.

Instantiating a Corda Embedder Object

To instantiate a Corda Embedder object, use code similar to the following:

CordaEmbedder myImage = new CordaEmbedder();

Setting the Server Information

Corda Embedder needs to know two Corda Server addresses: the address that the Web client uses to access Corda Server (externalServerAddress), and the address that Corda Embedder uses to access Corda Server (internalCommPortAddress).

Note: If you have trouble finding these values, ask your Corda Server administrator or refer to Identifying Server Addresses.

For example, if Corda Embedder communicates with the Corda Server at 10.0.1.1:2002 and Web clients request images from http://myserver.mycompany.com:2001, include the following in the code that generates the Corda image:

myImage.externalServerAddress = "http://myserver.mycompany.com:2001"
myImage.internalCommPortAddress = "10.0.1.1:2002"

Specifying Image Information

After specifying server address information, give Corda Embedder some information about the Corda image you want to embed.

There are numerous Corda Embedder commands to specify image information, which are consistent in all Web application environments. Thus, it is unnecessary to discuss each of these commands individually at this time.

The table below provides links to more information about Corda image features and components:

Topic	Refer To
Annotations	Data Annotations
Content Delivery / Presentation Control	Image Deployment Issues and Descriptive Text Settings
Data	Connecting to Data Files and Connecting to Databases
Drilldown	Building Drilldown
Graph or Map Customization	Dynamically Customizing Graphs and Maps
Image Size & Format	Changing the Image Format and Changing Image Size

Writing the Image to a Web Page

When you are ready to write the embedding HTML to a Web page, output the getEmbeddingHTML method to the Web page. For example, if you have instantiated a PrintWriter object named pw, use code similar to the following to output the embedding HTML:

pw.println(myImage.getEmbeddingHTML());

Compiling a Servlet

Make sure that CordaEmbedder.jar is in the classpath when compiling the servlet. If you do not know how to compile a servlet, refer to the documentation for the Web application server.

Complete Example Code

The example below demonstrates embedding a Corda image in a Java Servlet.

Note: To produce an example map instead of a graph, replace examples/bar.itxml with examples/map/australia_combo.itxml in the code designating the Image Template file.

Embedding a Corda Image in a Java Servlet

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import com.corda.CordaEmbedder;
 
public class example1 extends HttpServlet
{
 
       public void init(ServletConfig config)
       throws ServletException
       {
          super.init(config);
       }
        
       public void doPost(HttpServletRequest request, HttpServletResponse response)
       throws ServletException, IOException
       {
       }
        
       public void doGet(HttpServletRequest request, HttpServletResponse response)
       throws ServletException, IOException
       {
          PrintWriter pw = response.getWriter();
          response.setContentType("text/html");
           
          try
          {
             pw.println("<html>");
             pw.println("<head>");
             pw.println("<title>My First Embedded Image</title>");
             pw.println("</head>");
             pw.println("<body>");
             pw.println("<h1>Your image will appear below:</h1>");
              
             // Begin Corda Embedder Code
             CordaEmbedder myImage = new CordaEmbedder();
             myImage.externalServerAddress = "http://<server_address>:2001";
             myImage.internalCommPortAddress = "http://localhost:2002";
             myImage.imageTemplate = "image_templates\examples\bar.itxml";
             myImage.width = 600;
             myImage.height = 400;
             myImage.pcScript = "title.setText(Hello World)";
             pw.println(myImage.getEmbeddingHTML());
             // End Corda Embedder Code
              
          pw.println("</body>");
          pw.println("</html>");
          }
          catch(Exception exc)
          {
          }
       }
}

Note: This code catches any exceptions that may be generated as you embed the Corda image. You do not have to do this. The Corda Embedder itself does not throw any exceptions. However, the PrintWriter or the request object might throw an exception, so you might want to catch it. Besides, it's good coding practice to catch exceptions.