C调用Java：配置多jar包路径指南-优快云博客

本文详细介绍了如何在C程序中调用Java代码，特别是当Java程序依赖多个jar包时，如何正确设置`java.class.path`和`-Djava.ext.dirs`以指定jar包路径。通过编写C代码、制定makefile和组织Java代码，成功实现C与Java的交互，并在服务器上执行得到结果。

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c 调用 java 时，java 程序常常是依赖多个jar包的，关键是如何要告诉jvm jar包的路径。

先写c代码:

1 c代码

写调用JAVA 的C++ 代码(main.cpp)如下:

#include <iostream>
#include <jni.h>

#ifdef _WIN32
  #define PATH_SEPARATOR ';'
#else
  #define PATH_SEPARATOR ':'
#endif

using namespace std;


int main()
{

	JavaVMOption options[3];
	JNIEnv *env;
	JavaVM *jvm;
	JavaVMInitArgs vm_args;
	long status;
	jclass cls;
	jmethodID mid;
	jint square;
	jboolean not1;
	jobject jobj;

	options[0].optionString = "-Djava.class.path=/home/cInvokeJavaLinux/refjar";
	options[1].optionString="-verbose:jni";
	options[2].optionString="-Djava.ext.dirs=/home/cInvokeJavaLinux/refjar";
	
	
	vm_args.version =JNI_VERSION_1_6;// JNI_VERSION_1_2;
	vm_args.nOptions = 3;
	vm_args.options = options;



/*	options[0].optionString = "-Djava.class.path=.";
	vm_args.version =JNI_VERSION_1_6;// JNI_VERSION_1_2;
	vm_args.nOptions = 1;
	vm_args.options = options;
*/


	status = JNI_CreateJavaVM(&jvm, (void**)&env, &vm_args);
	/*
	if (status != JNI_ERR)
	{
		cls = env->FindClass("com/testJni/testDemo/C2java");
		if(cls !=0)
		{ 
			mid = env->GetStaticMethodID( cls, "add", "(II)I");
			if(mid !=0)
			{  
				square = env->CallStaticIntMethod( cls, mid, 5,5);
				std::cout << square << std::endl;
			}
			mid = env->GetMethodID(cls,"<init>","()V");
			if(mid !=0)
			{  
				jobj=env->NewObject(cls,mid);
				std::cout << "init ok" << std::endl;
			}
			mid = env->GetMethodID( cls, "judge","(Z)Z");
			if(mid !=0)
			{  
				not = env->CallBooleanMethod(jobj, mid, 1);
				if(!not){
					std::cout << "Boolean ok" << std::endl;
				}
			}

		}

		jvm->DestroyJavaVM();
		return 0;
	}*/
	if (status != JNI_ERR)
	{
		std::cout<<"JNI_CreateJavaVM  sucess"<<std::endl;

		cls = env->FindClass("V2ConfWebService");
		if(cls !=0)
		{ 
			mid = env->GetStaticMethodID( cls, "getWebServiceResultConfID", "()I");
			if(mid !=0)
			{  
				int  ret=env->CallStaticIntMethod( cls, mid);
				std::cout << "end CallStaticIntMethod ret=" << ret<<std::endl;
			}
			
			/*
			mid = env->GetMethodID(cls,"<init>","()V");
			if(mid !=0)
			{  
				jobj=env->NewObject(cls,mid);
				std::cout << "init ok" << std::endl;
			}
			mid = env->GetMethodID( cls, "judge","(Z)Z");
			if(mid !=0)
			{  
				not = env->CallBooleanMethod(jobj, mid, 1);
				if(!not){
					std::cout << "Boolean ok" << std::endl;
				}
			}
			*/

			

		}
		else
		{
			std::cout<<"calss V2ConfWebService  not found"<<std::endl;
		}

		jvm->DestroyJavaVM();
		return 0;
	}
	else
	{
		std::cout<<"JNI_CreateJavaVM  failed"<<std::endl;
		return -1;
	}

}

上面的代码中，

java.class.path=/home/cInvokeJavaLinux/refjar
指定Java代码编译的类的存放的路径，但是这个选项没法指定多个jar包的路径。
最关键的是要使用,-Djava.ext.dirs=/home/cInvokeJavaLinux/refjar
指定多个jar包的路径。
在/home/cInvokeJavaLinux/refjar目录中，我们把我们写的java 的代码和所有引用的第三方的jar包都放到了这个目录中。

1.2 c代码的makefile

all:test
clean:
	rm -rf  test
test:
	g++ -g   -o  test  main.cpp -I/usr/java/jdk1.7.0/include -I/usr/java/jdk1.7.0/include/linux/ -L/usr/java/jdk1.7.0/jre/lib/i386/client/ -ljvm

上面的makefile中的/usr/java/jdk1.7.0/jre/lib/i386/client/ 是libjvm.so库的路径。

2 java 代码

下面我们写java 代码。

import org.apache.axis.client.Service;
import org.apache.axis.client.Call;


public class V2ConfWebService {
	

	public static int  getWebServiceResultConfID() {
		
		   try {
	        	
	            int  retCode=-1;
	            
	            String endpoint = "http://192.168.84.1:11080/Conf/" +
	                    "services/ConferenceWebService?wsdl";
						
	
	            
	            String method = "getWebServiceResult";
	            
	            int number = 8000;
	            
	           
	            
	            Service service = new Service();
	             
	            Call call = (Call)service.createCall();
	            call.setTargetEndpointAddress(new java.net.URL(endpoint));
	            call.setOperationName(method);
	            call.getMessageContext().setUsername("v2com");
	            call.getMessageContext().setPassword("simple");
	            
       
	            //
	            String xml = 
	            "<?xml version='1.0' encoding='UTF-8'?>"+
	            "<Package confid='313151'  webservicepwd=''/>";
  
	         
	            Object[] s = new Object[]{number,xml,""};
	         
	            String result = (String) call.invoke(s);
	           
	            System.out.println(result);
	           // retCode= Integer.parseInt(result);
	            return 1984;
				
	        } catch (Exception ex) {
	        	
	            ex.printStackTrace();
	            System.err.println(ex.toString());
	            
	            return -1;
	        }
		   
		  
    }
	
	public static void  main(String[]  args ) {
	
		//public static void  getWebServiceResultConfID(String confid) {	
	        try {
	        	
	            int  retCode=-1;
	            
	            String endpoint = "http://192.168.84.1:11080/Conf/" +
	                    "services/ConferenceWebService?wsdl";
						
	            
	            String method = "getWebServiceResult";
	            
	            int number = 8000;
	            Service service = new Service();
	             
	            Call call = (Call)service.createCall();
	            call.setTargetEndpointAddress(new java.net.URL(endpoint));
	            call.setOperationName(method);
	            call.getMessageContext().setUsername("v2com");
	            call.getMessageContext().setPassword("simple");
	            
        
	            //
	            String xml = 
	            "<?xml version='1.0' encoding='UTF-8'?>"+
	            "<Package confid='313151'  webservicepwd=''/>";
   
	         
	            Object[] s = new Object[]{number,xml,""};
	         
	            String result = (String) call.invoke(s);
	           
	            System.out.println(result);
	          //  retCode= Integer.parseInt(result);
	            //return retCode;
	            
	         
				
	        } catch (Exception ex) {
	            ex.printStackTrace();
	            System.err.println(ex.toString());
	            
	          //  return -1;
	        }
	    }
	}

这个java 代码在 eclipse中编译后，把bin 中的V2ConfWebService.class 文件和引用的jar 包都拷贝到服务器上的
/home/cInvokeJavaLinux/refjar 目录。

3 编译执行

在/home/cInvokeJavaLinux目录中，执行make 编译得到test.

在写个脚本如下:

export LD_LIBRARY_PATH=/usr/java/jdk1.7.0/jre/lib/i386/client
./test

执行这个脚本就得到了C 调用JAVA 的结果。