Java Servlet上的空指针异常
我的DH密钥交换应用程序快完成了。我现在尝试在我的应用程序上验证我的客户端。 但是，我的服务器上不断出现空指针异常。我将问题追溯到我的大整数变量，但我没有发现任何问题 我正在尝试向客户端发送1或0的响应。 1表示已验证，0表示未验证 我将显示发生错误的部分 DHServlet.javaJava Servlet上的空指针异常,java,android,client-server,Java,Android,Client Server,我的DH密钥交换应用程序快完成了。我现在尝试在我的应用程序上验证我的客户端。 但是，我的服务器上不断出现空指针异常。我将问题追溯到我的大整数变量，但我没有发现任何问题 我正在尝试向客户端发送1或0的响应。 1表示已验证，0表示未验证 我将显示发生错误的部分 DHServlet.java public class DHServlet extends HttpServlet { private static final long serialVersionUID = 1L; private stat
public class DHServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
private static String pk2;
private static String pCValue;
private static String gCValue;
private static String sCValue;
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
// PrintWriter out2=response.getWriter();
DH getDH = new DH();
try {
String un,pw,pk;
Random randomGenerator = new Random();
long pValue = randomGenerator.nextInt(100000000);
long gValue = randomGenerator.nextInt(100000000);
boolean checkPrime = getDH.isPrime(pValue);
while(checkPrime == false)
{
long generatePValue2 = randomGenerator.nextInt(10000000);
boolean checkPrime2 = getDH.isPrime(generatePValue2);
if(checkPrime2==true)
{
pValue=generatePValue2;
break;
}
}
long checkSP = (pValue*2)+1;
boolean checkSafePrime = getDH.isPrime(checkSP);
while(checkSafePrime == false)
{
long generatePValue3 = randomGenerator.nextInt(100000000);
boolean checkSpInLoop = getDH.isPrime(generatePValue3);
long checkSP2 = (generatePValue3*2)+1;
boolean checkSafePrimeInLoop = getDH.isPrime(checkSP2);
if(checkSpInLoop == true && checkSafePrimeInLoop == true)
{
pValue = generatePValue3;
break;
}
}
while(gValue>pValue)
{
long gValue2=randomGenerator.nextInt(100000000);
if(gValue2<pValue)
{
gValue=gValue2;
break;
}
}
long getDivisor =(pValue-1)/2;
BigInteger bi1,bi2,bi3,bi4;
bi1=BigInteger.valueOf(getDivisor);
bi2=BigInteger.valueOf(pValue);
bi3=BigInteger.valueOf(gValue);
bi4=bi3.modPow(bi1,bi2);
long calculatedValue = bi4.longValue();
while(calculatedValue == 1)
{
long gValue3=randomGenerator.nextInt(100000000);
long getDivisorInLoop = (pValue-1)/2;
BigInteger bi5,bi6,bi7,bi8;
bi5=BigInteger.valueOf(getDivisorInLoop);
bi6=BigInteger.valueOf(pValue);
bi7=BigInteger.valueOf(gValue3);
bi8=bi7.modPow(bi5, bi6);
long calculatedValueInLoop = bi8.longValue();
if(calculatedValueInLoop != 1)
{
gValue=gValue3;
break;
}
}
BigInteger generatorValue,primeValue,skA,biPKA;
generatorValue = BigInteger.valueOf(gValue);
primeValue = BigInteger.valueOf(pValue);
long secretKeyA = getDH.generateSKA();
skA=BigInteger.valueOf(secretKeyA);
biPKA =getDH.generatePkA(generatorValue, primeValue, secretKeyA);
System.out.println("The public key of server is "+biPKA);
System.out.println("The generator value is "+generatorValue);
System.out.println("The prime value is "+primeValue);
System.out.println("the secret key of the server is "+skA);
long PKA = biPKA.longValue();
out.print(pValue+":"+gValue+":"+PKA);
pk2=biPKA.toString();
pCValue=primeValue.toString();
gCValue=generatorValue.toString();
sCValue=skA.toString();
} finally {
out.close();
}
}
protected void processRequest2(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
DH getDH2=new DH();
String un,pw,pk,shareK;
try
{
pk=request.getParameter("publicK");
un=request.getParameter("username");
pw=request.getParameter("password");
shareK=request.getParameter("sharedKey");
String publicKey = pk;
BigInteger biPK,biSK,biP,sKey;
biPK = new BigInteger(publicKey);
biSK = new BigInteger(sCValue);
biP = new BigInteger(pCValue);
System.out.println(biPK);
sKey = getDH2.calculateSharedKey(biPK, biSK, biP);
String sharedServerKey = (sKey.toString()).trim();
System.out.println("the shared key is "+sharedServerKey);
if(un.equalsIgnoreCase("larry")&& pw.equals("123") && sharedServerKey == shareK)
{
out.print(1);
}
else
{
out.print(0);
}
}finally
{
out.close();
}
}
/**
* @see HttpServlet#HttpServlet()
*/
public DHServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
processRequest(request,response);
processRequest2(request,response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
processRequest2(request,response);
}
如果（gValue2您的stacktrace说您的一个大整数有问题（pk、un或pw中的一个为null）那么例外情况很明显：
pk=request.getParameter("publicK");
un=request.getParameter("username");
pw=request.getParameter("password");
shareK=request.getParameter("sharedKey");
BigInteger biPK,biSK,biP,sKey;
biPK = new BigInteger(pk);
biSK = new BigInteger(sCValue);
biP = new BigInteger(pCValue);
pksCValuepCValuenullnull点异常
pk=request.getParameter("publicK");
un=request.getParameter("username");
pw=request.getParameter("password");
顺便问一下，变量sCValue
和pCValue
在哪里初始化？在这种情况下，会发生NullPointerException，因为您将null
的值传递给BigInteger
的构造函数
stacktrace告诉您调用它的行号：DHServlet.java:158
假设线路如下所示
biPK = new BigInteger(pk);
然后，pk
为null。您可能正在使用null
字符串实例化biginger
。任何或所有请求参数都是null
pk=request.getParameter("publicK");
un=request.getParameter("username");
pw=request.getParameter("password");
其中一个变量：pk、sCValue或pCValue
是null
，因为我不知道Servlet
中的第158行是什么
你不能用null作为参数实例化biginger
。它是主类上的一个全局变量。我将编辑顶部的代码部分，然后检查pk
是否为null，并逐行调试每个变量。这就是那一行，但是我如何知道该变量是否为null。我打印了该变量，其中包含一个value.如果我错了，请纠正我，我在doGet方法上对processRequest2进行了注释。代码工作正常，但是当它未注释时，会发生空指针异常。这是因为吗？@Clearner88是的，因为如果您查看堆栈跟踪，您会发现您的问题在DHServlet
的第158行这一行是？嗯，这很奇怪。我用isEmpty方法检查了所有的值。它们都返回false这是行biPK=new biginger（publicKey）；这意味着publicKey
为null