java.io.IOException: The input doesn't contain any classes. Did you specify the proper '-injars' opt

问题场景

---

在使用Maven + Proguard打包项目进行混淆时，提示以下错误：

[proguard] ProGuard, version 4.4
 [proguard] Reading input...
 [proguard] java.io.IOException: The input doesn't contain any classes. Did you specify the proper '-injars' options?
 [proguard]     at proguard.InputReader.execute(InputReader.java:91)
 [proguard]     at proguard.ProGuard.readInput(ProGuard.java:195)
 [proguard]     at proguard.ProGuard.execute(ProGuard.java:78)
 [proguard]     at proguard.ProGuard.main(ProGuard.java:499)

问题分析

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缺少injars配置项！
-injars {class_path} 指定要处理的应用程序jar,war,ear和目录

解决方案

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添加injars配置项，由于是Web项目，所以这里指定的是war

<injar>${project.build.finalName}.war</injar>

完整示例：

            <plugin>
                <groupId>com.pyx4me</groupId>
                <artifactId>proguard-maven-plugin</artifactId>
                <version>2.0.4</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>proguard</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <obfuscate>true</obfuscate>
                    <proguardInclude>${basedir}/proguard.conf</proguardInclude>
                    <!-- 添加依赖，这里你可以按你的需要修改 -->
                    <libs>
                        <lib>${java.home}/lib/rt.jar</lib>
                        <lib>lib/jsp-api.jar</lib>
                        <lib>lib/servlet-api.jar</lib>
                    </libs>
                    <addMavenDescriptor>false</addMavenDescriptor>
                    <injar>${project.build.finalName}.war</injar>
                    <outjar>${project.build.finalName}-pg.war</outjar>
                    <outputDirectory>${project.build.directory}</outputDirectory>
                </configuration>
                <dependencies> 
                    <!-- 使用4.4版本来混淆 -->
                    <dependency>
                        <groupId>net.sf.proguard</groupId>
                        <artifactId>proguard</artifactId>  
                        <version>4.4</version>
                        <scope>runtime</scope>
                    </dependency>
                </dependencies>
            </plugin>