Requirement of JSTL when studying Java EE
Does I need to study JSTL in java EE. I'm studying java EE, does studying JSTL gives any advantage if it is not a part of java EE. Thanks in advance.
See also questions close to this topic
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Determine type of empty wildcard collection (e.g. List<? extends Number>)
I have a
Collectionof elements. When theCollectionis populated, it's easy to get the first element and work out what type it is. But when theCollectionis empty, I can't work out how do to it.Example below:
public static void main(final String args[]) { typer(Collections.singletonList(Integer.valueOf(0))); typer(Collections.singletonList(Double.valueOf(0))); typer(Collections.<Integer> emptyList()); } private static void typer(final List<? extends Number> list) { if (list.isEmpty()) { System.out.println(list.getClass()); } else { System.out.println(list.get(0).getClass()); } }The output produced is:
class java.lang.Integer class java.lang.Double class java.util.Collections$EmptyList -
Have I achieved linear time complexity O(n) for this array comparison algorithm?
I am writing a method that compares 2 arrays, a and b, and returns "YES" if all the elements of b are present in a, and "NO" otherwise. The algorithm must have linear time complexity.
I have a solution that works but I am confused about the time complexity. I have used a single foreach to check if the first element in a is an element of b and if it is not, I increment the search index of a and check again. I understand this is O(n).
If the element exists, I then use a while loop to check all the elements of b against the single element of a to see if the element is in both arrays.
Here's the method:
public String subArrayProblem_LinearTime(int[] a, int[]b) { int aIndex = 0; int elementsFound = 0; while (aIndex < a.length) { int bIndex = 0; int value = a[aIndex]; boolean elementExists = false; for (int i : b) { if (value == i) { elementExists = true; break; } } if (elementExists) { while (bIndex < b.length) { if (b[bIndex] == a[aIndex]) { elementsFound++; aIndex++; break; } else { bIndex++; } } } else{ aIndex++; } } return elementsFound == b.length ? "YES" : "NO"; }My question is; have I just mimicked a nested for loop and achieved O(n^2) or is this O(n)? I think it's O(n) but am not sure as I'm still fairly new to this topic.
Many thanks :)
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Trying to optimise my java code with loop, but I get a weird result
Someone can help me to use a loop for reducing this code, but when i do it, I have a weird result when i try print the result, I get the memory adress object of my class. This is my code: ==========================
elementGraphe[] tableau= { new coutChemin(getInt(CDG.getSommet().get(0)), getInt(CDG.getSommetVoisin().get(0)),getInt(CDG.getListeCout().get(0)) ), new coutChemin(getInt(CDG.getSommet().get(1)), getInt(CDG.getSommetVoisin().get(1)),getInt(CDG.getListeCout().get(1)) ), new coutChemin(getInt(CDG.getSommet().get(2)), getInt(CDG.getSommetVoisin().get(2)),getInt(CDG.getListeCout().get(2)) ), new coutChemin(getInt(CDG.getSommet().get(3)), getInt(CDG.getSommetVoisin().get(3)),getInt(CDG.getListeCout().get(3)) ), new coutChemin(Integer.parseInt(CDG.getSommet().get(4)), Integer.parseInt(CDG.getSommetVoisin().get(4)),Integer.parseInt(CDG.getListeCout().get(4)) ), new coutChemin(Integer.parseInt(CDG.getSommet().get(5)), Integer.parseInt(CDG.getSommetVoisin().get(5)),Integer.parseInt(CDG.getListeCout().get(5)) ), new coutChemin(Integer.parseInt(CDG.getSommet().get(6)), Integer.parseInt(CDG.getSommetVoisin().get(6)),Integer.parseInt(CDG.getListeCout().get(6)) ), new coutChemin(Integer.parseInt(CDG.getSommet().get(7)), Integer.parseInt(CDG.getSommetVoisin().get(7)),Integer.parseInt(CDG.getListeCout().get(7)) ), new coutChemin(Integer.parseInt(CDG.getSommet().get(8)), Integer.parseInt(CDG.getSommetVoisin().get(8)),Integer.parseInt(CDG.getListeCout().get(8)) ), new coutChemin(Integer.parseInt(CDG.getSommet().get(9)), Integer.parseInt(CDG.getSommetVoisin().get(9)),Integer.parseInt(CDG.getListeCout().get(9)) ), new coutChemin(Integer.parseInt(CDG.getSommet().get(10)), Integer.parseInt(CDG.getSommetVoisin().get(10)),Integer.parseInt(CDG.getListeCout().get(10)) ), new coutChemin(Integer.parseInt(CDG.getSommet().get(11)), Integer.parseInt(CDG.getSommetVoisin().get(11)),Integer.parseInt(CDG.getListeCout().get(11))), new coutChemin(Integer.parseInt(CDG.getSommet().get(12)), Integer.parseInt(CDG.getSommetVoisin().get(12)),Integer.parseInt(CDG.getListeCout().get(12))), new coutChemin(Integer.parseInt(CDG.getSommet().get(13)), Integer.parseInt(CDG.getSommetVoisin().get(13)),Integer.parseInt(CDG.getListeCout().get(13))), new coutChemin(Integer.parseInt(CDG.getSommet().get(14)), Integer.parseInt(CDG.getSommetVoisin().get(14)),Integer.parseInt(CDG.getListeCout().get(14))), new coutChemin(Integer.parseInt(CDG.getSommet().get(15)), Integer.parseInt(CDG.getSommetVoisin().get(15)),Integer.parseInt(CDG.getListeCout().get(15))), new coutChemin(Integer.parseInt(CDG.getSommet().get(16)), Integer.parseInt(CDG.getSommetVoisin().get(16)),Integer.parseInt(CDG.getListeCout().get(16))), new coutChemin(Integer.parseInt(CDG.getSommet().get(17)), Integer.parseInt(CDG.getSommetVoisin().get(17)),Integer.parseInt(CDG.getListeCout().get(17))), new coutChemin(Integer.parseInt(CDG.getSommet().get(18)), Integer.parseInt(CDG.getSommetVoisin().get(18)),Integer.parseInt(CDG.getListeCout().get(18))), new coutChemin(Integer.parseInt(CDG.getSommet().get(19)), Integer.parseInt(CDG.getSommetVoisin().get(19)),Integer.parseInt(CDG.getListeCout().get(19))), }; =============================================== like this : ======================================== public void Tabchemin() { for(int i=0;i<20;i++) { chemin1 = new coutChemin[] { new coutChemin(getInt(CDG.getSommet().get(i).toString()), getInt(CDG.getSommetVoisin().get(i).toString()), getInt(CDG.getListeCout().get(i).toString()))}; } } ==================================== But when I use this loop, I get a weird result: [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922 [LalgorithmeDeDjjikstra.coutChemin;@7852e922I search google, I see we can Arry.toString(Tableau), method toString(),...
public String toString(Object obj){ return getClass().getName() + '@' + Integer.toHexString(hashCode()); }But I get the same result. Thanks in advance, sorry for my english and I'm a beginner in java.
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Better programming JSP one page vs multiple pages
JSP Application programming Which is better Coding in minimal number of JSP pages with multiple if conditions For example inserting sales,costs,expenses,customers,products etc with an if statement with variables.
if(variableValue=='Sales' { Sales insert code } else if(variableValue='Costs' { costs insert code }Creating multiple pages.
salesinsert.jsp costinsert.jsp etc
which is better and good programming. what are the advantages and disadvantages in short term and long term Performance Maintanence Migration to a different technology stack (such as java to python)
I know it is not good to write application logic in JSP. But unfortunately i cannot change it now. Both the ways i am coding logic in jsp page itself
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Passing values from one servlet to another
I have a jsp with value String filesrno = "testvalue". Also I have a form I am submitting on this jsp.
<form action="Sortable"id="myform" method="post"> <input type="hidden" id="no1" name="filesrno"> <input type="hidden" id="no2" name="totalcount"> </form>where Sortable is another Servlet and values are passed to this servlet 2. I have the same value in Sortable Servlet too accessed using getParameter. I want to get this value in Servlet 3 named as TempServlet. Please help me get the value in the tempServpet using Servlet or JSP
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The server JSP not found the java class
I am Sergio de la Torre, I am working with JSP serverlt but I have got a problem, the server JSP catch an exception, Tells Me you can not find the class of Java, because it may be due to this error, I need some help please, thank you very much.
Here's the exception:
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how to retain the drop down value using 'selected' attribute after submitting the html form which is within the servlet class itself
public class ServletApplication extends HttpServlet { private static final long serialVersionUID = 1L;
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { int number1 , number2, number3; /* * Setting the content type to html */ response.setContentType("text/html"); /* * Getting the printWriter object */ PrintWriter pr = response.getWriter(); /* * Html form in the servlet class itself */ pr.println("<!DOCTYPE html>"); pr.println("<html>"); pr.println("<head>"); pr.println("<tittle>CALCULATOR</tittle"); pr.println("</head>"); pr.println("<body>"); pr.println("<form action = 'ServletApplication' method = 'Get'>"); /* * Retain the values that are entered */ String n1 = request.getParameter("number1") != null?request.getParameter("number1"):""; String n2 = request.getParameter("number2") != null?request.getParameter("number2"):""; pr.println("<br>number1:<input type='text' name= 'number1' value="+n1+" ><br>"); pr.println("<br>number2:<input type='text' name= 'number2' value="+n2+" ><br><br>"); pr.println("operation:<select name='options'>"); pr.println("<option name='add' >add</option>"); pr.println("<option name='multiply' >multiply</option>"); pr.println("<option name='subtract' >subtract</option>"); pr.println("<option name='divide' >divide</option>"); pr.println("</select><br><br>"); pr.println("<button type= 'submit' value = 'process' name = 'button'>process</button> "); pr.println("<button type= 'submit' value = 'cancel' name = 'button'>cancel</button> "); pr.println("</form>"); pr.println("</body>"); pr.println("</html>"); /* * Avoiding the null format exception */ if (request.getParameter("number2") != null) { String button = request.getParameter("button"); if (button.equals("process")) { number1 = Integer.parseInt(request.getParameter("number1")); number2 = Integer.parseInt(request.getParameter("number2")); String select = request.getParameter("options"); /* * Switch case to select from the drop-down */ switch (select) { case "add": number3 = number1 + number2; pr.println("<br>result:<input type = 'text' value =" + number3 + " />"); break; case "multiply": number3 = number1 * number2; pr.println("<br>result:<input type = 'text' value =" + number3 + " />"); break; case "divide": try { number3 = number1 / number2; pr.println("<br>result:<input type = 'text' value =" + number3 + " />"); } catch(ArithmeticException e) { pr.println("<br>result:<input type = 'text' value ='cant divide by zero' />"); } break; case "subtract": number3 = number1 - number2; pr.println("<br>result:<input type = 'text' value =" + number3 + " />"); break; } } else response.sendRedirect("ServletApplication"); } }}
how can i retain the value of the drop down after submitting the form, everything is done in this servlet class alone, am not using an html file or jsp or anything. i want to run this in the servlet class itself. i don't want to use jsp or javaScript or php. i have tried using ternary if within the println statement but its not working , please help
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Can a web application be developed using hybrid technologies?
Is it possible to develop a web application using a mix of technologies like servlet and nodejs? Using servlets somewhere and nodejs at some other place when required.
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Read message are delivered again when client connect back in standalone HornetQ
I have a setup a standalone Hornet queue which running locally. For a testing purpose i have a created a standalone JMS consumer which read the message after every 5 second. I am facing a strange behaviour in Consumer side, when my client connect and read all the messages from queue and if i forced shutdown this(without proper closing a session/connection) then next time when i start this consumer it again start reading old messages from queue. Here is my consumer example:
while (true) { ClientMessage messageReceived = messageConsumer.receive(1000); if (messageReceived != null && messageReceived.getStringProperty(MESSAGE_PROPERTY_NAME) != null) { System.out.println("Received JMS TextMessage:" + messageReceived.getStringProperty(MESSAGE_PROPERTY_NAME)); messageReceived.acknowledge(); } Thread.sleep(500); }Can someone tell me why it is working like this way and what kind of configuration should i use in client/server side so that if a message read by consumer it will delete this from a queue.
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Dependency injection through constructor does not work for EJB bean
My app is being deployed on to IBM WebSphere. I have a simple service and I'd like to know how dependency injection works in this case.
// stateless EJB @Stateless public class UserService { private UserDAO userDAO; // btw, UserDAO is stateless EJB as well @Inject public UserService(UserDAO userDAO) { this.userDAO = userDAO; } // biz methods ... }It fails with the following error:
[ERROR ] CWWKZ0002E: An exception occurred while starting the application my-app. The exception message was: com.ibm.ws.container.service.state.StateChangeException: com.ibm.ws.cdi.CDIException: com.ibm.wsspi.injectionengine.InjectionException: com.ibm.ejs.container.EJBConfigurationException: EJB class com.demo.app.UserService must have a public constructor that takes no parameters
I remember there was something in EJB spec that says:
the class must have a public constructor that takes no parametersand it makes sense for me that the bean instance is first instantiated by the container and afterward dependency injection is done.On the other hand, I've found this in WELD docs:
First, the container calls the bean constructor (the default constructor or the one annotated @Inject), to obtain an instance of the bean.
And I am confused a little bit, why my EJB cannot be instantiated.
How is the EJB instance being created and dependencies injected when we have constructor injection point?
Any ideas? :)
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How to get configured retryable/skippable exceptions in jsr352
I'd like to write some generic batch listeners to log out some useful information of all batches configured in my application. To do so I'd like to get the configured skippable/retryable exceptions from batch configuration. However I did not find any API for that. Is there a way to retrieve this configuration independant of the jsr352 implementation?
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How to make dropdown value show a table in jquery?
I have a dropdown, but when user clicks on a dropdown value it shows a json format results like this:
[{"id":"11111","label":"PROGRAMMER","value":"1111"}. Instead of that json - I want to show a table that I have below in jquery. Is it possible in this case? I just want to show my table when user select a dropdown value. thanks for the help.Here is my code:
<table class="table"> <tbody> <tr> <th></th> <c:forEach var="stepNumber" begin="1" end="#{testBean.jobEntity.stepSize}" varStatus="loop"> <c:if test="${loop.index lt 9}"> <th class="right-header">Step #{stepNumber}</th> </c:if> </c:forEach> </tr> <c:forEach items="#{testBean.jobEntity.jobRows}" var="jobRow"> <tr class="odd"> <td class="left-header">#{jobRow.rateType}</td> <c:forEach items="#{jobRow.steps}" var="step" varStatus="loop"> <c:if test="${loop.index lt 8}"> <td class="left-header">#{step.amount}</td> </c:if> </c:forEach> </tr> </c:forEach> </c:if> </div> </f:view> <script type="text/javascript"> $( "#sJobClass" ).on("change", function() { var jobClassCd = $(this).val(); if (jobClassCd !== 0) { $.post('http://localhost:8080/myApp/JobSearchItem.xhtml', function(data) { $('#results').append(JSON.stringify(data) + '<br/><br/>'); }); } }); </script>html with jstl / jsf tags:
<select class="selectMenuSize" id="sJobClass" name="sJobClass"> <option value="">Choose</option> <c:forEach items="#{myBean.jobSearchItems}" var="searchItem"> <option value="#{searchItem.getSearchValue()}" id="searchInputField" name="searchInput">#{searchItem.toString()}</option> </c:forEach> </select> -
c:if is not working with html <a href> link?
I have a link that needs to appear on the webpage but for some reason,
c:ifdoes not work. Below you can find the code that contains my java and myc:ifcode. Thank you for the help.Here is my code:
<c:if test="#{testBean.jobEntity.validURLConnection}"> <a href="#{testBean.jobEntity.pGradeDescriptionLink}" target="_blank">[ Visit Website ]</a> </c:if>Java:
public String getPGradeDescriptionLink() { return payGDescriptionLink; } private void setPGradeDescriptionLink(String pGrade) { this.pGradeDescriptionLink = "http://private_domain.com/pgrade/" + pGrade + ".pdf"; } public boolean isValidURLConnection() throws IOException { URL url = null; try { url = new URL(this.pGradeDescriptionLink ); } catch (MalformedURLException e) { e.printStackTrace(); } HttpURLConnection connection = (HttpURLConnection) url.openConnection(); try { connection.setRequestMethod("GET"); connection.connect(); return connection.getResponseCode() == 200; } catch (IOException e) { e.printStackTrace(); } return false; } -
request mapping to return html div(tabs) in jsp page in spring boot project with jstl
I am trying to map the request from controller to a div(tab) in a jsp file. I researched but found only ways to do that in thymleaf using "th:classappend" using ternary operators. Below is my controller code.
@RequestMapping("/myaccount") public String myaccount() { return "myaccount"; } @RequestMapping("/login") public String login(Model model) { model.addAttribute("classActiveLogin", true); return "myaccount"; }My html code
<div class="tabs"> <div class="tab-button-outer"> <ul id="tab-button"> <li><a href="#tab01">Create Account</a></li> <li><a href="#tab02">User Login</a></li> <li><a href="#tab03">Reset Password</a></li> </ul> </div> <div class="tab-select-outer"> <select id="tab-select"> <li><a href="#tab01">Create Account</a></li> <li><a href="#tab02">User Login</a></li> <li><a href="#tab03">Reset Password</a></li> </select> </div> <div id="tab01" class="tab-contents ${classActiveLogin}? 'in active'"> <form action="/newUser" method="post"> username:<br> <input type="text" name="username" size="35" required><br> email:<br> <input type="email" name="email" id="email" size="35" required><br> <br> <input type="submit" name="createnewaccount" Value="createnewaccount"><br> </form> </div>Below is the screenshot of my myaccount page.
This is the screenshot of my jsp page.
What I want here is when I type localhost:8080/login I want the User Login tab to activate. Thanks in advance
