How to Recover Source Code and Rebuild a Java WAR Project from Scratch

In this tutorial we assume a software development team faces a client‑driven change request but only has the deployed WAR file of a Java web application and no original source code.

The original application is built with Spring, exposes REST endpoints to generate PDF reports from MySQL data, and is packaged as a WAR.

Priority 1: Obtain the Application Source

First we retrieve the WAR file from the production server, rename it to .jar (since WAR and JAR are both ZIP‑based archives), and prepare it for decompilation.

Priority 2: WAR Reverse Engineering

Several free decompilers can turn Java bytecode back into source code, such as Bytecode Viewer, Java Decompiler, Fernflower, and Procyon. We chose Bytecode Viewer for its GUI and support for JAR inputs.

Using Bytecode Viewer we decompile the classes inside the renamed archive. The tool’s output is shown in the image below:

Priority 3: Restore the Web Application Structure

After decompilation we unpack the JAR to reveal the original directory layout. The expected structure includes:

WEB-INF

web.xml

lib (all dependency JARs)

classes

applicationContext.xml

log4j.properties

config.properties

com (package directories with .class files)

META-INF

MANIFEST.MF

maven

com.app

Application

pom.properties

pom.xml

images (form.png, img.png, other PNGs)

templates (HTML report templates)

index.jsp

We then map these files to a standard Maven web project layout:

src/main/java – all decompiled Java source files.

src/main/resources – configuration files such as applicationContext.xml, log4j.properties, and config.properties.

src/main/webapp – WEB-INF/web.xml, static images, HTML templates, and index.jsp.

Priority 4: Assemble the Project

With the source code and resources placed in the Maven directories, the project now contains the following structure:

src
  main
    java
      com\... (all packages)
    resources
      applicationContext.xml
      config.properties
      log4j.properties
    webapp
      WEB-INF
        web.xml
      images
        form.png
        img.png
        *.png
      templates
        *.html
      index.jsp
pom.xml

Running mvn clean install builds the application successfully.

Result

The recovered source code and rebuilt project were delivered to the client, enabling further maintenance and customization of the web application.