Reloading/Refreshing Spring configuration file without restarting the servlet container

Question

How can I refresh Spring configuration file without restarting my servlet container?

I am looking for a solution other than JRebel.

Answer 1

Well, it can be useful to perform such a context reload while testing your app.

You can try the refresh method of one of the AbstractRefreshableApplicationContext class: it won't refresh your previously instanciated beans, but next call on the context will return refreshed beans.

import java.io.File;
import java.io.IOException;

import org.apache.commons.io.FileUtils;
import org.springframework.context.support.FileSystemXmlApplicationContext;

public class ReloadSpringContext {

    final static String header = "\n" +
        "\n";

    final static String contextA =
        "\n" +
            "\t\t\n" +
        "";

    final static String contextB =
        "\n" +
            "\t\t\n" +
        "";

    public static void main(String[] args) throws IOException {
        //create a single context file
        final File contextFile = File.createTempFile("testSpringContext", ".xml");

        //write the first context into it
        FileUtils.writeStringToFile(contextFile, header + contextA);

        //create a spring context
        FileSystemXmlApplicationContext context = new FileSystemXmlApplicationContext(
            new String[]{contextFile.getPath()}
        );

        //echo the bean 'test' on stdout
        System.out.println(context.getBean("test"));

        //write the second context into it
        FileUtils.writeStringToFile(contextFile, header + contextB);

        //refresh the context
        context.refresh();

        //echo the bean 'test' on stdout
        System.out.println(context.getBean("test"));
    }

}

And you get this result

fromContextA
fromContextB

Another way to achieve this (and maybe a more simple one) is to use the Refreshable Bean feature of Spring 2.5+ With dynamic language (groovy, etc) and spring you can even change your bean behavior. Have a look to the spring reference for dynamic language:

24.3.1.2. Refreshable beans

One of the (if not the) most compelling value adds of the dynamic language support in Spring is the 'refreshable bean' feature.

A refreshable bean is a dynamic-language-backed bean that with a small amount of configuration, a dynamic-language-backed bean can monitor changes in its underlying source file resource, and then reload itself when the dynamic language source file is changed (for example when a developer edits and saves changes to the file on the filesystem).