Protecting Spring Boot Applications with Classfinal Maven Plugin: Code Encryption and Machine‑Bound Execution

Scenario: A project needs to be deployed on a client’s server without exposing source code, requiring the production startup package to be protected against decompilation.

Solution Overview:

First approach – code obfuscation : Use proguard-maven-plugin, which works for single‑module projects but becomes complex in multi‑module setups due to intricate configuration and potential errors.

Second approach – code encryption : Use classfinal-maven-plugin, which simplifies protection by encrypting class files, YAML/properties files, and dependent JARs, and supports machine‑bound execution.

Project Setup: Add the following plugin configuration to the pom.xml after the spring-boot-maven-plugin section:

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
        <plugin>
            <!-- classfinal-maven-plugin configuration -->
            <groupId>net.roseboy</groupId>
            <artifactId>classfinal-maven-plugin</artifactId>
            <version>1.2.1</version>
            <configuration>
                <password>#</password> <!-- # means no password needed at runtime -->
                <excludes>org.spring</excludes>
                <packages>${groupId}</packages> <!-- packages to encrypt, comma‑separated -->
                <cfgfiles>application.yml,application-dev.yml</cfgfiles>
                <libjars>hutool-all.jar</libjars>
                <code>xxxx</code> <!-- optional machine code -->
            </configuration>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>classFinal</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

Startup Methods:

No‑password start :

java -javaagent:xxx-encrypted.jar -jar xxx-encrypted.jar

Password‑protected start :

java -javaagent:xxx-encrypted.jar='-pwd=密码' -jar xxx-encrypted.jar

Decompilation Effect: After encryption, method bodies are cleared while parameters and annotations remain, allowing Swagger documentation to work; decompiled code shows only method signatures and annotations, with no method implementation, and decryption occurs entirely in memory without leaving files.

Machine‑Bound Execution: Download classfinal-fatjar-1.2.1.jar, run java -jar classfinal-fatjar-1.2.1.jar -C to generate a machine code, then place that code into the plugin’s code element so the packaged JAR can run only on that specific machine.