CODEWITHSUNDEEP
javarestservlets
Thorn
Thorn

Reputation: 4057

Accessing a Servlet Initialization Parameter from REST resource

I have a JAX-RS REST web app that is used to store and retrieve files for a desktop client. I will be deploying this in two different environments on two different servers, so I would like the path where the files will be stored to be configured outside of the code.

I know how to read initialization parameters (in web.xml) from a Servlet. Can I do something similar for a REST resource class? If I could read from some other file inside the WEB-INF directory, that should work fine too.

Here is the code I'm working with:

import javax.ws.rs.*;
import java.io.*;

@Path("/upload")
public class UploadSchedule {

    static String path = "/home/proctor/data/schoolData/";
    //I would like to store the path value in web.xml
    @PUT
    @Path("/pxml/{id}/")
    @Consumes("text/xml")   @Produces("text/plain")
    public String receiveSchedule(@PathParam("id") final Integer schoolID, String content) {
        if (saveFile(schoolID, "schedule.pxml", content))
            return schoolID + " saved assignment schedule."
        else
            return "Error writing schedule. ("+content.length()+" Bytes)";
    }

    /**
     * Receives and stores the CSV file faculty list. The location on the server
     * is not directly associated with the request URI. 
     * @param schoolID
     * @param content
     * @return a String confirmation message.
     */
    @POST
    @Path("/faculty/{id}/")
    @Consumes("text/plain")     @Produces("text/plain")
    public String receiveFaculty(@PathParam("id") final Integer schoolID, String content) {
        if (saveFile(schoolID, "faculty.csv", content))
            return schoolID + " saved faculty.";
        else
            return "Error writing faculty file.(" +content.length()+ " Bytes)";

    }
    //more methods like these

    /**
     * Saves content sent from the user to the specified filename. 
     * The directory is determined by the static field in this class and 
     * by the school id.
     * @param id SchoolID
     * @param filename  location to save content
     */
    private boolean saveFile(int id, String filename, String content) {
        File saveDirectory = (new File(path + id));
        if (!saveDirectory.exists()) {
            //create the directory since it isn't there yet.
            if (!saveDirectory.mkdir()) 
                return false;
        }
        File saveFile = new File(saveDirectory, filename);
        try(FileWriter writer = new FileWriter(saveFile)) {
            writer.write(content);
            return true;
        } catch (IOException ioe) {
            return false;
        } 
    }
}

Upvotes: 0

Views: 3450

Answers (2)

Thorn
Thorn

Reputation: 4057

While obtaining init parameters from web.xml seems like a common task, it took me quite some time to get to the bottom of this and find a solution that worked. To save others from my frustration, let me post my solution. I am using the Jersey implementation, namely com.sun.jersey.spi.container.servlet.ServletContainer Perhaps other REST implementations can access web.xml init params using ServletContext but in spite of documentation leading me to believe this would work, it did not.

I needed to use the following instead: @Context ResourceConfig context; This is listed as one of the fields in my Resource class. Then within one of my resource methods, I was able to access the web.xml init parameter with the following:

String uploadDirectory = (String) context.getProperty("dataStoragePath");

Where the property refers to the web.xml file :

  <init-param>
      <param-name>dataStoragePath</param-name>
      <param-value>C:/ztestServer</param-value>
  </init-param>

Surprisingly, when I used @Context ServletContext context; I discovered that the context object really referenced an ApplicationContextFacade. I could see no way to get through that Facade and access the information I cared about. I printed out the parameter map and it showed me that the only parameters this object was aware of:

    java.util.Enumeration<String> params = context.getInitParameterNames();
    while(params.hasMoreElements())
        System.out.println(params.nextElement());

output:

 com.sun.faces.forceLoadConfiguration
 com.sun.faces.validateXml

Upvotes: 3

FUD
FUD

Reputation: 5184

First you have to get the servlet context using 

@Context 
ServletContext context;

Then inside your rest resource

context.getInitParameter("praram-name")

Upvotes: 0

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