Javassist修改jar包字节码

1.添加maven依赖

<dependency>
    <groupId>org.javassist</groupId>
    <artifactId>javassist</artifactId>
    <version>${javaassist.version}</version>
</dependency>
 
<properties>
    <javaassist.version>3.21.0-GA</javaassist.version>
</properties>

2.编写修改方法

 public static void removeWatermark() throws NotFoundException, CannotCompileException, IOException {
        ClassPool.getDefault().insertClassPath("D:\\software\\57-file\\fast-preview-master\\code\\lib\\aspose-words.jar"); // jar包的绝对路径
        CtClass targetClass = ClassPool.getDefault().getCtClass("com.aspose.words.zzZE0"); //类路径
        //这里是因为我要修改多个方法得返回值，所以填写多个修改就好
        CtMethod targetMethod = targetClass.getDeclaredMethod("zzZ4h"); //方法路径
        CtMethod targetMethod1 = targetClass.getDeclaredMethod("zzZ4g"); //方法路径
        targetMethod.setBody("{return 1;}"); //修改方法体，始终返回1
        targetMethod1.setBody("{return 1;}"); //修改方法体，始终返回1
        targetClass.writeFile("D:\\aaaaa"); //保存修改，内容为保存的路径。
    }

    public static void main(String[] args) throws IOException, CannotCompileException, NotFoundException {
        removeWatermark();
    }

3.最后将生成得class文件替换jar包中得文件即可。