无法使用execl（）启动jar [英] Unable to launch jar with execl()

问题描述

我得到一个 decrypt.jar 和 encrypt.jar 文件，用于在传输之前准备文件。

当我启动终端并输入：

  / usr / bin / java -jar /path/to/jar/decrypt.jar 
  

 未指定输入文件
  

这是OK！瓶子工作。现在在我的代码中，当我用execl（）启动jar，我得到这个作为输出：

 错误：找不到或加载主类util.decrypt.jar 
解密器退出与0 
  

请注意，问题这里是java试图启动类，这实际上是路径的jar（路径是util / decrypt.jar，并执行它作为一个类util.decrypt.jar）

我的代码：

  bool decrypt_file（const std :: string& file）{
 int result ; 
 int pipefd [2]; 
 FILE * cmd_output; 
 char buf [1024]; 
 int status; 
 
 result = pipe（pipefd）; 
 if（result< 0）{
 throwpipe error！; 
} 
 
 pid_t pid = fork（）; / *创建一个子进程* / 
 const std :: string decryptJar =util / decrypt.jar; 
 int ex; 
 if（！fileExists（decryptJar））throw文件解密器不存在！ fork（）失败！
 
 switch（pid）{
 case -1：/ *错误* / 
 #ifdef _DEBUG 
 std :: cout< \\\
; 
 #endif 
 return false; 
 case 0：/ *子进程* / 
 dup2（pipefd [1]，STDOUT_FILENO）; / *重复写入结束到stdout * / 
 close（pipefd [0]）; 
 close（pipefd [1]）; 
 
 // getJava（）返回/ usr / bin / java
 ex = execl（Config :: getInstance（）.getJava（）。c_str（），-jar decryptJar.c_str（），file.c_str（），NULL）; / *执行程序* / 
 #ifdef _DEBUG 
 std :: cout< execl（）failed！returned<< ex<<，errno =<< errno<<\ n / * execl不返回除非有错误* / 
 // todo如果errno是2，java在系统上没有找到，让用户知道！ 
 #endif 
 return false; 
默认值：/ *父进程* / 
 int status; 
 close（pipefd [1]）; / *关闭写管道结束* / 
 cmd_output = fdopen（pipefd [0]，r）; 
 #ifdef _DEBUG 
 if（fgets（buf，sizeof buf，cmd_output））{
 std :: string str（buf）; 
 std :: cout<<OUTPUT：<< str<<\\\
; 
} 
 #endif 
 while（！WIFEXITED（status））{
 waitpid（pid，& status，0）; / *等待进程完成* / 
} 
 
 #ifdef _DEBUG 
 std :: cout<< 解密器退出与< WEXITSTATUS（status）<< \\\
; 
 #endif 
 return true; 
} 
} 
  

jar中的manifest是正确的by eclipse）：

  Manifest-Version：1.0 
 Class-Path：。 
 Main-Class：com。{...}。解密
  

：

尝试将路径更改为jar的绝对路径没有解决问题。

  const std :: string decryptJar = workingDir（）+/util/decrypt.jar; 
  

解决方案

已解决

从我身边的愚蠢的错误，第一个参数应该按照惯例总是可执行文件的路径。

  ex = execl（Config :: getInstance（）。getJava（）。c_str（），-jar，decryptJar。 c_str（），file.c_str（），NULL）; / *执行程序* / 
  

应为

  ex = execl（Config :: getInstance（）。getJava（）。c_str（），decrypt.jar.c_str（），-jar，decryptJar.c_str c_str（），NULL）; / *执行程序* / 
  

发生了什么事情是java以-jar因此我的命令实际上是

  java pathToJar input 
   
 
而不是
  java -jar pathToJar input 
  
编辑：修正后的程式码片段：
  bool decrypt_file（const std :: string& javaPath，const std :: string& file）{
 int result，status; 
 int pipefd [2]; 
 FILE * cmd_output; 
 char buf [1024]; 
 int ex; 
 const std :: string decryptJar = workingDir（）+/util/decrypt.jar; 
 
 result = pipe（pipefd）; 
 if（result< 0）{
 throwpipe error！; 
} 
 
 pid_t pid = fork（）; / *创建子进程* / 
 if（！fileExists（decryptJar））throw文件解密器不存在！ fork（）失败！
 
 switch（pid）{
 case -1：/ * Error * / 
 #ifdef _DEBUG 
 std :: cout< \\\
; 
 #endif 
 return false; 
 case 0：/ *子进程* / 
 dup2（pipefd [1]，STDOUT_FILENO）; / *重复写入结束到stdout * / 
 close（pipefd [0]）; 
 close（pipefd [1]）; 
 
 ex = execl（javaPath.c_str（），decrypt.jar.c_str（），-jar，decryptJar.c_str（），file.c_str（），NULL）; / *执行程序* / 
 #ifdef _DEBUG 
 std :: cout< execl（）failed！returned<< ex<<，errno =<< errno<<\ n / * execl不返回除非有错误* / 
 #endif 
 if（errno == 2）{
 std :: cout<<JAVA NOT FOUND！和/或如果配置文件中的路径指向正确的java安装！\\\
\\\
; 
} 
 return false; 
 default：/ *父进程* / 
 close（pipefd [1]）; / *关闭写管道结束* / 
 cmd_output = fdopen（pipefd [0]，r）; 
 #ifdef _DEBUG 
 if（fgets（buf，sizeof buf，cmd_output））{
 std :: string str（buf）; 
 if（str！=OK）
 std :: cout<<--- DECRYPT OUTPUT：<< str<<\\\
 
} 
 #endif 
 while（！WIFEXITED（status））{
 waitpid（pid，& status，0）; / *等待进程完成* / 
} 
 
 #ifdef _DEBUG 
 std :: cout<< 解密器退出与< WEXITSTATUS（status）<< \\\
; 
 #endif 
 return true; 
} 
} 
  
 
I was given a decrypt.jar and encrypt.jar file, which are used to prepare files before transmitting.

When I launch the terminal and type:
/usr/bin/java -jar /path/to/jar/decrypt.jar
I get the output:
No input file specified
Which is OK! The jar works. Now in my code, when I launch the jar with execl(), I get this as output:
Error: Could not find or load main class util.decrypt.jar
Decryptor exited with 0
Notice that the issue here is that java tried to launch the class which is actually the path to the jar (the path is util/decrypt.jar, and it executed it as a class util.decrypt.jar)

My code:
bool decrypt_file(const std::string& file) {
    int result;
    int pipefd[2];
    FILE *cmd_output;
    char buf[1024];
    int status;

    result = pipe(pipefd);
    if (result < 0) {
        throw "pipe error!";
    }

    pid_t pid = fork(); /* Create a child process */
    const std::string decryptJar = "util/decrypt.jar";
    int ex;
    if ( !fileExists(decryptJar) ) throw "File decryptor does not exist!";

    switch (pid) {
        case -1: /* Error */
#ifdef _DEBUG
            std::cout<<"fork() failed!\n";
#endif
            return false;
        case 0: /* Child process */
            dup2(pipefd[1], STDOUT_FILENO); /* Duplicate writing end to stdout */
            close(pipefd[0]);
            close(pipefd[1]);

            //getJava() returns "/usr/bin/java"
            ex = execl(Config::getInstance().getJava().c_str(), "-jar", decryptJar.c_str(), file.c_str(), NULL); /* Execute the program */
#ifdef _DEBUG
            std::cout << "execl() failed! returned "<<ex<<", errno = "<<errno<<"\n"; /* execl doesn't return unless there's an error */
            //todo if errno is 2, java was not found on the system, let the user know!
#endif
            return false;
        default: /* Parent process */
            int status;
            close(pipefd[1]); /* Close writing end of pipe */
            cmd_output = fdopen(pipefd[0], "r");
#ifdef _DEBUG
            if (fgets(buf, sizeof buf, cmd_output)) {
                std::string str(buf);
                std::cout<<"OUTPUT: "<<str<<"\n";
            }
#endif
            while (!WIFEXITED(status)) {
                waitpid(pid, &status, 0); /* Wait for the process to complete */
            }

#ifdef _DEBUG
            std::cout << "Decryptor exited with " << WEXITSTATUS(status) << "\n";
#endif
            return true;
    }
}
The manifest inside the jar is correct (it was generated by eclipse):
Manifest-Version: 1.0
Class-Path: .
Main-Class: com.{...}.Decryptor
Add:  

Trying to change the path to the absolute path of the jar didn't fix the problem.
const std::string decryptJar = workingDir() + "/util/decrypt.jar";

解决方案
Solved

Stupid mistake from my side, the first argument should, by convention, always be the path to the executable.

So
ex = execl(Config::getInstance().getJava().c_str(), "-jar", decryptJar.c_str(), file.c_str(), NULL); /* Execute the program */
Should be
ex = execl(Config::getInstance().getJava().c_str(), decryptJar.c_str(), "-jar", decryptJar.c_str(), file.c_str(), NULL); /* Execute the program */
What happened is that java took "-jar" as the path, thus my command was actually
java pathToJar input
instead of
java -jar pathToJar input
Edit: the corrected code snippet:
bool decrypt_file(const std::string& javaPath, const std::string& file) {
        int result, status;
        int pipefd[2];
        FILE *cmd_output;
        char buf[1024];
        int ex;
        const std::string decryptJar = workingDir() + "/util/decrypt.jar";

        result = pipe(pipefd);
        if (result < 0) {
            throw "pipe error!";
        }

        pid_t pid = fork(); /* Create a child process */
        if ( !fileExists(decryptJar) ) throw "File decryptor does not exist!";

        switch (pid) {
            case -1: /* Error */
    #ifdef _DEBUG
                std::cout<<"fork() failed!\n";
    #endif
                return false;
            case 0: /* Child process */
                dup2(pipefd[1], STDOUT_FILENO); /* Duplicate writing end to stdout */
                close(pipefd[0]);
                close(pipefd[1]);

                ex = execl(javaPath.c_str(), decryptJar.c_str(), "-jar", decryptJar.c_str(), file.c_str(), NULL); /* Execute the program */     
    #ifdef _DEBUG
                std::cout << "execl() failed! returned "<<ex<<", errno = "<<errno<<"\n"; /* execl doesn't return unless there's an error */
    #endif
                if ( errno == 2 ) {
                    std::cout<<"JAVA NOT FOUND! Check if java is installed and/or if the path in the config file points to a correct java installation!\n\n";
                }
                return false;
            default: /* Parent process */
                close(pipefd[1]); /* Close writing end of pipe */
                cmd_output = fdopen(pipefd[0], "r");
    #ifdef _DEBUG
                if (fgets(buf, sizeof buf, cmd_output)) {
                    std::string str(buf);
                    if ( str != "OK" )
                        std::cout<<"---DECRYPT OUTPUT: "<<str<<"\n";
                }
    #endif
                while (!WIFEXITED(status)) {
                    waitpid(pid, &status, 0); /* Wait for the process to complete */
                }

    #ifdef _DEBUG
                std::cout << "Decryptor exited with " << WEXITSTATUS(status) << "\n";
    #endif
                return true;
        }
    }


                        
这篇关于无法使用execl（）启动jar的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！