我有一个登录Web应用程序。
每当我登录时，该请求都必须通过validate Servlet进行验证，并且必须转发到admin.jsp
一切都很好，除了我得到了java.lang.IllegalStateException这个异常。
码：
/*
* DEVELOPER : SURAJ GAUTAM
* CAMPUS: SHANKERDEV
* FACULTY: BIM
* COMPANY : UNKNOWN IT COMPANY
*/
package com.suraj.technepbankapplication;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
*
* @author Suraj Gautam
*/
@WebServlet(name = "validate", urlPatterns = {"/validate"})
public class validate extends HttpServlet {
DataBean bean = new DataBean();
int count = 0;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//the form inputted is sent to the Databean Class
settingValue(req.getParameter("userid"), req.getParameter("password"));
try {
if (!isValid(req, resp)) {
req.getRequestDispatcher("/index.jsp").forward(req, resp);
} else if (bean.getUserId().equals("admin")) {
req.getRequestDispatcher("/admin.jsp").forward(req, resp);
} else {
req.getRequestDispatcher("/afterlogin.jsp").forward(req, resp);
}
} catch (SQLException | ClassNotFoundException ex) {
System.out.println(ex.getMessage());
}
}
public boolean isValid(HttpServletRequest req, HttpServletResponse resp) throws SQLException, ServletException, IOException, ClassNotFoundException {
String userId = req.getParameter("userid");
String password = req.getParameter("password");
if (userId.length() <4 || password.length() < 4) {
return false;
} else {
return loginValidate(req, resp);
}
}
//setting DataBean class Value
public void settingValue(String userid, String password) {
bean.setUserId(userid);
bean.setPassword(password);
}
public boolean loginValidate(HttpServletRequest req, HttpServletResponse resp) throws SQLException, ServletException, IOException, ClassNotFoundException {
String url = "jdbc:mysql://localhost/technep";
String user = "root";
String password = "";
String query = "SELECT id, password FROM technep_login";
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection(url, user, password);
PreparedStatement preparedStatement = conn.prepareStatement(query);
ResultSet resultSet = preparedStatement.executeQuery();
while (resultSet.next()) {
//working till here
if (resultSet.getString("id").trim().equals(bean.getUserId()) && resultSet.getString("password").trim()
.equals(bean.getPassword())) {
count = 1;
break;
}
}
if (count == 1) {
return true;
} else {
return false;
}
}
}
输出：
Warning: StandardWrapperValve[jsp]: Servlet.service() for servlet jsp threw exception
java.lang.IllegalStateException: getOutputStream() has already been called for this response
at org.apache.catalina.connector.Response.getWriter(Response.java:777)
at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:224)
at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:195)
at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:188)
at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:240)
at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:185)
at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:137)
at org.apache.jsp.DBimage_jsp._jspService(DBimage_jsp.java:93)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:111)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:411)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:473)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:377)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:416)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:283)
at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:206)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:180)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:283)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:200)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:132)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:111)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:536)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:591)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPoo l.java:571)
at java.lang.Thread.run(Thread.java:745)
最佳答案
抱歉，根据您提供的stacktrace，此问题无法回答：servlet甚至没有出现在stacktrace中，因此该servlet可能不是问题，或者您忽略了“根本原因” stacktrace。
此外，您的代码还有很多问题，您应该真正学习servlet开发的基础教程。这些无法在stackoverflow的单个答案中得到纠正
将bean用作servlet成员的方式将导致灾难（争用情况）。 Servlet中不得包含成员变量（状态）。
您自己亲自进行身份验证-您显然不应该这样做，这是一个很好解决的问题
最重要的是，您显然将明文密码存储在数据库中，并且始终枚举整个用户数据库，而不仅仅是获取单个值（想象有多个用户...）
从此代码中，我假设只需手动进入/afterlogin.jsp或/admin.jsp也可以跳过验证。
方法的参数也是可争论的，并且会导致难以维护的实现。
这是不完整的列表。
关于java - 为什么在调用validate servlet时出现java.lang.IllegalStateException？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/39199681/