共有6个文件/类：mainLaptop，Send，c_app，StreamTest，make file和ap.text。
我正在尝试获取在c文件中处理的数据并将其传递给我的java文件中的变量。按照本教程中的“PIPE WITH STRINGS”部分进行操作：http://www.jonathanbeard.io/tutorials/CtoJava
首先，我打开终端并输入
1 make StreamTest
2 make c_app
3 java -cp . StreamTest
4 ./c_app
执行时，我看到“JAVA SIDE !!”接下来是终端中c进程的总数，数量和平均值（以及由于我的修改而导致的一些错误）
然后在eclipse中我在eclipse中运行StreamTest
Eclipse输出此
JAVA SIDE:
[x] Sent ''Leonardo
[x] Sent ''Raphael
[x] Sent ''Donatello
[x] Sent ''Michelangelo
但是我需要输出这个
JAVA SIDE:
[x] Sent 'Total: 4953, Integers: 1000, Average: 4.9530'Leonardo
[x] Sent 'Total: 4953, Integers: 1000, Average: 4.9530'Raphael
[x] Sent 'Total: 4953, Integers: 1000, Average: 4.9530'Donatello
[x] Sent 'Total: 4953, Integers: 1000, Average: 4.9530'Michelangelo
这是c代码
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <inttypes.h>
#define DEBUG 0
#define BUFFER 4096
//open ap.txt for text input
static const char* exFile = "ap.txt";
static char inputBuffer[BUFFER];
int main(int argc, const char** argv)
{
FILE *fp = fopen(exFile,"r");
/*check and see if the pointer is null in otherwords see if the memory
location refered to by fp is set...no memory location should be zero
if you want to reference it
Here are some good ways to do this other than the way I did it below:
if(!fp) {do error}
if(fp == NULL) {do error}
and then there's the way I did it below
*/
if(fp == 0){
fprintf(stderr,"Null pointer exception, check file name.\n");
exit(-1);
}
//check and see if an error occured during open
const int err = ferror(fp);
if(err != 0){
/* void perror(const char* err) returns specific error message to string attached. */
const char* errMessage = strcat("Something bad happened while opening file ",exFile);
perror(errMessage);
}
#if (DEBUG == 1)
else{
fprintf(stderr,"Success opening file!!\n");
}
#endif
setbuf(fp,inputBuffer); //set a buffer for input
uint64_t *num = (uint64_t*) malloc(sizeof(uint64_t));
uint64_t total = 0;
uint64_t n = 0;
//test for eof
/*
feof(*fp) - returns a boolean true if at end of file and false otherwise
*/
while(!feof(fp)){
//fscanf returns the number of items it converted using %llu, if it's not equal to 1 we don't want to continue
if(fscanf(fp,"%"PRIu64"",num)!=1)
break; //you could do a lot of stuff here as far as error handling but basically something bad has happened
total+= *num; //add to total the value at memory location num
n++;
#if (DEBUG == 1)
fprintf(stderr,"line number %"PRIu64"\n",n);
#endif
}
free(num);
const double average = (double) total / (double) n;
//close the inputfile
fclose(fp);
//declare our outputfile, use a pipe in this case to a java process
//we open a java process for this process to pipe to, also it is
//technically a bi-directional pipe so we can use any of the modifiers
//like r/w/r+/etc
static const char* outFile = "java -cp . StreamTest";
FILE *fp_out = popen(outFile,"w");
//setbuf(fp_out,outputBuffer);
fprintf(fp_out,"Total: %"PRIu64", Integers: %"PRIu64", Average:
%.4f\n",total,n,average);
/*
int fflush(*fp) pushes any data in the buffer to be written
the return value returns 0 if successful or !=0 if an error
occurs....remember return values in C often equal exceptions
*/
fflush(fp_out);
/* int */
fclose(fp_out);
return 1;
}
这是make文件
CC ?=gcc
JCC ?= javac
FLAGS ?= -Wall -O2
JFLAGS ?= -g -verbose
all: c_app StreamTest
c_app: c_app.c
$(CC) $(FLAGS) -o c_app c_app.c
StreamTest: StreamTest.java
$(JCC) $(JFLAGS) StreamTest.java $(LIBS)
clean:
rm -f c_app StreamTest.class
ap.text文件只是一堆数字
StreamTest
import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
public class StreamTest
{
private static final int buffer = 4096;
public static void main(String[] args) throws Exception
{
String pass=null;
InputStream is = null;
BufferedInputStream bis = null;
try
{
bis = new BufferedInputStream(System.in,buffer);
StringBuilder sb = new StringBuilder();
//sb.append((char)bis.read());
while(bis.available() > 0){
sb.append((char)bis.read());
}
pass = sb.toString();
System.out.println("JAVA SIDE: "+pass);
bis.close();
}
catch(IOException ex)
{
}
finally
{
}
//pass = "hi";
mainLaptop.main(pass);
}
}
这是我在StreamTest类中调用的mainLaptop类。
public class mainLaptop
{
public static void main(String arg) throws Exception
{
//Timing out? change the IP!
String ip="192.168.137.127";
String Pi1Q1="Leonardo";
String Pi1Q2="Raphael";
String Pi2Q3="Donatello";
String Pi2Q4="Michelangelo";
String pass=arg;
Send.send(ip, Pi1Q1, pass);
Send.send(ip, Pi1Q2, pass);
Send.send(ip, Pi2Q3, pass);
Send.send(ip, Pi2Q4, pass);
/* Recv.recv(ip, Pi1Q1);
Recv.recv(ip, Pi1Q2);
Recv.recv(ip, Pi2Q3);
Recv.recv(ip, Pi2Q4);*/
}
}
这是我在mainLaptop类中调用的发送代码
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
public class Send
{
public static void send(String ip, String Q, String pass) throws
Exception
{
ConnectionFactory factory = new ConnectionFactory();
//set connection info
factory.setHost(ip);
factory.setUsername("test");
factory.setPassword("test");
//create connection
Connection connection = factory.newConnection();
//create channel
Channel channel = connection.createChannel();
//publish message
// int a = 1;
//while (a!=0)
{
channel.queueDeclare(Q, false, false, false, null);
//for(int i=1; i<=2; i++)
{
//String message = pass;
channel.basicPublish("", Q, null, pass.getBytes("UTF-8"));
System.out.println(" [x] Sent '" + pass + "'" + Q);
}
//a--;
}
//SHUT IT ALL DOWN!
channel.close();
connection.close();
}
}
使用
import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
public class StreamTest{
private static final int buffer = 4096;
static String pass;
public static void main(String[] args)
{
InputStream is = null;
BufferedInputStream bis = null;
BufferedReader bir = null;
try
{
bis = new BufferedInputStream(System.in,buffer);
StringBuilder sb = new StringBuilder();
while ((bir.readLine()) != null)
{
// Do something here. Who knows
}
/*while(bis.available() > 0){
sb.append((char)bis.read());
}*/
/*int b;
while ((b = bis.read()) != -1)
{
// do something with 'b'
sb.append((char)b);
}*/
pass=sb.toString();
System.out.println("JAVA SIDE: "+pass);
bir.close();
bis.close();
}
catch(IOException ex)
{
}
finally{
}
try {
mainLaptop.main(pass);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
答案 0 :(得分：2)
available()不是对流结束的测试。见Javadoc。摆脱它，并在read()返回-1时终止读取循环，或者使用BufferedReader.readLine()并在它返回null时终止。
并且不要忽视例外。
编辑为了让点回家，修改后的循环应为：
int b;
while ((b = bis.read()) != -1)
{
sb.append((char)b);
}
或更可能
String line;
while ((line = bufferedReader.readLine()) != null)
{
// Do something with 'line', other than merely appending it to a StringBuffer
}