How to Obfuscate Java Projects Using ProGuard and Maven

Compilation

Compilation simply runs the code, turning .java files into .class files.

Decompilation

Decompilation reverses compiled .class files inside jar/war packages back to readable source code, often using tools like JD‑GUI.

Obfuscation

Obfuscation is a technique to make decompiled code unreadable, protecting the original source.

Implementation

The process consists of two main steps:

Step 1: Create a ProGuard configuration file

Add a proguard.cfg file in the project root with options such as target Java version, disabling shrinking and optimization, preserving class member names, keeping annotations, and specifying classes to keep un‑obfuscated.

# Specify Java version
-target 1.8
# Disable shrinking
-dontshrink
# Disable optimization
-dontoptimize
# Do not use mixed‑case class names
-dontusemixedcaseclassnames
# Use unique class member names
-useuniqueclassmembernames
# Adapt class strings
-adaptclassstrings
# Keep attributes
-keepattributes Exceptions,InnerClasses,Signature,Deprecated,SourceFile,LineNumberTable,*Annotation*,EnclosingMethod
# Keep interface names
-keepnames interface ** { *; }
# Keep parameter names
-keepparameternames
# Keep enum members
-keepclassmembers enum * { *; }
# Keep Spring annotations
-keepclassmembers class * {
    @org.springframework.context.annotation.Bean *;
    @org.springframework.beans.factory.annotation.Autowired *;
    @org.springframework.beans.factory.annotation.Value *;
    @org.springframework.stereotype.Service *;
    @org.springframework.stereotype.Component *;
}
# Ignore warnings and notes
-ignorewarnings
-dontnote
# Print configuration
-printconfiguration
-keep public class com.example.myproguarddemo.MyproguarddemoApplication {
    public static void main(java.lang.String[]);
}

Step 2: Add ProGuard Maven plugin to pom.xml

Insert the following plugin configuration inside the <build> section to run ProGuard during the Maven package phase, specifying input and output jars, enabling obfuscation, and including the proguard.cfg file.

<build>
    <plugins>
        <plugin>
            <groupId>com.github.wvengen</groupId>
            <artifactId>proguard-maven-plugin</artifactId>
            <version>2.6.0</version>
            <executions>
                <!-- Executes ProGuard when running mvn package -->
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>proguard</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <injar>${project.build.finalName}.jar</injar>
                <outjar>${project.build.finalName}.jar</outjar>
                <obfuscate>true</obfuscate>
                <proguardInclude>${project.basedir}/proguard.cfg</proguardInclude>
                <libs>
                    <lib>${java.home}/lib/rt.jar</lib>
                    <lib>${java.home}/lib/jce.jar</lib>
                    <lib>${java.home}/lib/jsse.jar</lib>
                </libs>
                <inLibsFilter>!META-INF/**,!META-INF/versions/9/**.class</inLibsFilter>
                <outputDirectory>${project.basedir}/target</outputDirectory>
                <options/>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <executions>
                <execution>
                    <goals>
                        <goal>repackage</goal>
                    </goals>
                    <configuration>
                        <mainClass>com.example.myproguarddemo.MyproguarddemoApplication</mainClass>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

After configuring, run mvn package ; the build process will compile, obfuscate, and package the jar, producing an obfuscated artifact that is harder to reverse‑engineer.

Finally, verify the generated jar and observe the obfuscation effect.