What Is a WAR File?

A WAR is a ZIP file with a specific directory structure. It contains:

• WEB-INF/web.xml — the deployment descriptor (servlet mappings, listeners, filters)
• WEB-INF/classes/ — compiled Java .class files
• WEB-INF/lib/ — all dependency JARs bundled into the app
• META-INF/MANIFEST.MF — archive metadata
• Static resources (HTML, CSS, JS, images) in the root or subdirectories

The WEB-INF/ directory is special: files inside it are never served directly to clients by the servlet container.

Method 1: List Contents Without Extracting

jar -tvf myapp.war

Flags: -t (table/list), -v (verbose), -f (filename). Pipe through grep to find specific files:

jar -tvf myapp.war | grep "web.xml"
jar -tvf myapp.war | grep "\.properties"
jar -tvf myapp.war | grep "spring"

Example output:

     0 Thu Nov 30 12:00:00 EST 2023 META-INF/
   106 Thu Nov 30 12:00:00 EST 2023 META-INF/MANIFEST.MF
     0 Thu Nov 30 12:00:00 EST 2023 WEB-INF/
   742 Thu Nov 30 12:00:00 EST 2023 WEB-INF/web.xml
  4096 Thu Nov 30 12:00:00 EST 2023 WEB-INF/classes/com/example/MyServlet.class
 12345 Thu Nov 30 12:00:00 EST 2023 WEB-INF/lib/spring-core-5.3.20.jar

Method 2: Extract Everything

jar -xvf myapp.war

To extract into a specific folder:

mkdir -p extracted/myapp
cd extracted/myapp
jar -xvf ../../myapp.war

Method 3: Extract a Single File

# Extract just web.xml
jar -xvf myapp.war WEB-INF/web.xml

# Extract a specific class file
jar -xvf myapp.war WEB-INF/classes/com/example/MyServlet.class

# Extract a properties file
jar -xvf myapp.war WEB-INF/classes/application.properties

Method 4: Use unzip

Since WAR files are ZIP archives, unzip works and is often faster for large files:

# List contents (no extraction)
unzip -l myapp.war

# Extract everything
unzip myapp.war -d extracted/

# Extract a single file
unzip myapp.war WEB-INF/web.xml

# Extract all .properties files
unzip myapp.war "WEB-INF/classes/*.properties" -d config/

Typical WAR File Structure

myapp.war
├── META-INF/
│   └── MANIFEST.MF
├── WEB-INF/
│   ├── web.xml              ← deployment descriptor
│   ├── classes/             ← compiled .class files
│   │   ├── com/example/MyServlet.class
│   │   └── application.properties
│   └── lib/                 ← dependency JARs
│       ├── spring-core.jar
│       └── hibernate-core.jar
├── index.html               ← publicly accessible
├── css/
└── js/

How to Build a WAR File

With Maven — add <packaging>war</packaging> to your pom.xml, then:

mvn clean package
# WAR created at target/myapp.war

With Gradle — apply the war plugin in build.gradle, then:

./gradlew war
# WAR created at build/libs/myapp.war

Viewing Class File Contents

To inspect a .class file's bytecode (after extracting it):

# Show method signatures
javap WEB-INF/classes/com/example/MyServlet.class

# Show full bytecode disassembly
javap -c WEB-INF/classes/com/example/MyServlet.class

For human-readable source code, use a Java decompiler like CFR.

Platform Support

Quick Reference

jar -tvf myapp.war                          # list contents
jar -tvf myapp.war | grep web.xml           # find a specific file
jar -xvf myapp.war                          # extract everything
jar -xvf myapp.war WEB-INF/web.xml          # extract one file
unzip -l myapp.war                          # list with unzip
unzip myapp.war -d output/                  # extract to a folder