Error package javax servlet http



error: package javax.servlet.http doesn’t exist

  • I want compile and run servlet whose response object prints html tags which contains welcome message to user in form of html page.
    The code of WelcomeServletMesssage.java
    Placed location:C:\Program Files\Apache Software Foundation\Tomcat 7.0\webapps\ROOT\WEB-INF\classes\WelcomeServletMesssage.java

    Googled error, found I should create new user variable to set path for servlet-api.jar so then it can be used.
    In environment variables—> user variables
    I created new user variable, and set Variable name: CLASSPATH and Variable value: C:\Program Files\Apache Software Foundation\Tomcat 7.0\lib\ where my servlet-api.jar resides but still it gives same error. can somebody help me how to figure out this error..

    Being Java programmer.

  • Being Java programmer.

  • Being Java programmer.

  • Being Java programmer.

  • If you go copying library jars into your projects, you are probably wasting disk space, and potentially creating defective webapps. If you copy library jars into the lib directory of your JDK, they may not work because the JDK security won’t recognized their contents as being authorized for that location.

    To compile a program using a JDBC jar or servlet-api jar from the command line, add the jar file path(s) to the classpath on the javac command line. If you are using an IDE, you can usually set an equivalent in the project configuration dialog. In Eclipse, for example, I can assign a symbolic name to those jars and tell my project to use that name to locate the jars (and their contained classes) when the IDE compiles my source code.

    Blitzlügen — Lies or information broadcast, but when called out the broadcaster does little or nothing is done to correct them, thus allowing those who wish to believe to accept them as truth.

    Lügensturm — A barrage of Blitzlügen fired in such quick succession that it is essentially impossible to correct them all.

  • As Be careful relying on the CLASSPATH too much.

    I thought to use command line then
    My servlet is WelcomeServletMesssage.java is at location C:\Program Files\Apache Software Foundation\Tomcat 7.0\webapps\FirstServletApp\WEB-INF\classes\WelcomeServletMesssage.java

    I compiled it successfully in these 3 ways:

    Go to the folder where WelcomeServletMesssage.java is placed i.e. C:\Program Files\Apache Software Foundation\Tomcat 7.0\webapps\FirstServletApp\WEB-INF\classes\
    Then set CLASSPATH = C:\Program Files\Apache Software Foundation\Tomcat 7.0\lib\servlet-api.jar
    Then javac myservlet.java

    Javac –classpath “servlet-api.jar with its location” “my WelcomeServletMesssage.java with its location”
    Whole command becomes like this:
    Javac –classpath “C:\Program Files\Apache Software Foundation\Tomcat 7.0\lib\servlet-api.jar” “C:\Program Files\Apache Software Foundation\Tomcat 7.0\webapps\FirstServletApp\WEB-INF\classes\ WelcomeServletMesssage.java”

    Go to location where WelcomeServletMesssage.java is placed ( I used batch file to go to this location directly ) i.e.C:\Program Files\Apache Software Foundation\Tomcat 7.0\webapps\FirstServletApp\WEB-INF\classes\ then set classpath
    Whole command becomes like this:
    C:\Program Files\Apache Software Foundation\Tomcat 7.0\webapps\FirstServletApp\WEB-INF\classes\ javac –classpath C:\Program Files\Apache Software Foundation\Tomcat 7.0\lib\servlet-api.jar WelcomeServletMesssage.java

    Correct me If I’m wrong using command line to compile my WelcomeServletMesssage.java..
    Thank you so much Tim, Bear and Aditya for replying.

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    Problem with javax.servlet

  • I have a problem with javax.servlet. A part of my dependencie tree lookes like

    [INFO] +- io.micrometer:micrometer-registry-prometheus:jar:1.1.5:runtime
    [INFO] | \- io.prometheus:simpleclient_common:jar:0.5.0:runtime
    [INFO] | \- io.prometheus:simpleclient:jar:0.6.0:runtime
    [INFO] +- io.dropwizard.metrics:metrics-core:jar:4.1.0:compile
    [INFO] +- org.springframework.boot:spring-boot-starter-undertow:jar:2.1.6.RELEASE:compile
    [INFO] | +- io.undertow:undertow-core:jar:2.0.21.Final:compile
    [INFO] | | +- org.jboss.xnio:xnio-api:jar:3.3.8.Final:compile
    [INFO] | | \- org.jboss.xnio:xnio-nio:jar:3.3.8.Final:runtime
    [INFO] | +- io.undertow:undertow-servlet:jar:2.0.21.Final:compile
    [INFO] | | \- org.jboss.spec.javax.annotation:jboss-annotations-api_1.2_spec:jar:1.0.2.Final:compile
    [INFO] | +- io.undertow:undertow-websockets-jsr:jar:2.0.21.Final:compile
    [INFO] | | \- org.jboss.spec.javax.websocket:jboss-websocket-api_1.1_spec:jar:1.1.4.Final:compile
    [INFO] | +- javax.servlet:javax.servlet-api:jar:4.0.1:compile
    [INFO] | \- org.glassfish:javax.el:jar:3.0.0:compile
    [INFO] \- org.springframework.boot:spring-boot-devtools:jar:2.1.6.RELEASE:compile
    [INFO] ————————————————————————
    [INFO] BUILD SUCCESS

    The main thing here is that you can see that the javax.servlet is in the tree

    In the pom I defined a java.version.

    The fact is that I have installed java 11 on my new laptop and of course in the pom I first used version 11.

    When I build with version 11 I get the error shown here under. This is of course a part of the messages

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    Учебное пособие по исключениям и обработке ошибок сервлета

    Некоторое время назад я написал пост об обработке исключений в Java, но когда дело доходит до веб-приложения, нам нужно больше, чем обычная обработка исключений в Java.

    Сервлет Исключение

    Если вы заметили, что методы doGet () и doPost () ServletException и IOException , давайте посмотрим, что произойдет, когда мы выбросим эти исключения из нашего приложения. Я напишу простой сервлет, который выдаст исключение ServletException.

    MyExceptionServlet.java

    Теперь, когда мы вызываем этот сервлет через браузер методом GET, мы получаем ответ, как на картинке ниже.

    Поскольку браузер понимает только HTML, когда наше приложение генерирует исключение, контейнер сервлета обрабатывает исключение и генерирует HTML-ответ. Эта логика специфична для контейнера сервлетов, я использую tomcat и получаю эту страницу с ошибкой, но если вы будете использовать некоторые другие серверы, такие как JBoss или Glassfish, вы можете получить другой HTML-ответ об ошибке.

    Проблема с этим ответом заключается в том, что он не имеет значения для пользователя. Кроме того, он показывает пользователям наши классы приложений и информацию о сервере, что не имеет смысла для пользователя и не очень хорошо с точки зрения безопасности.

    Ошибка сервлета

    Я уверен, что вы, должно быть, увидели ошибку 404, когда пытались найти URL, который не существует. Давайте посмотрим, как наш контейнер сервлетов отвечает на ошибку 404. Если мы отправим запрос на неверный URL, мы получим ответ HTML, как показано на рисунке ниже.

    Опять же, это общий HTML-код, сгенерированный сервером от нашего имени и не имеющий никакой ценности для пользователя.

    Исключение сервлета и обработка ошибок

    Servlet API обеспечивает поддержку настраиваемых сервлетов Exception и Error Handler, которые мы можем настроить в дескрипторе развертывания. Целью этих сервлетов является обработка Exception или Error, возникающих в приложении, и отправка HTML-ответа, который будет полезен для пользователя. Мы можем предоставить ссылку на домашнюю страницу приложения или некоторые детали, чтобы сообщить пользователю, что пошло не так.

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    Поэтому прежде всего нам нужно создать собственный сервлет Exception and Error Handler. У нас может быть несколько сервлетов обработки исключений и ошибок для приложения, но для простоты я создам один сервлет и использую его как для исключений, так и для ошибок.

    Источник

    Servlet Exception and Error Handling Example Tutorial

    While we believe that this content benefits our community, we have not yet thoroughly reviewed it. If you have any suggestions for improvements, please let us know by clicking the “report an issue“ button at the bottom of the tutorial.

    Today we will look into Servlet Exception and Error Handling. Sometime back I wrote a post about Exception Handling in Java but when it comes to web application, we need more than normal exception handling in java.

    Servlet Exception

    If you notice, doGet() and doPost() methods throw javax.servlet.ServletException and IOException , let’s see what happens when we throw these exception from our application. I will write a simple servlet that will throw the ServletException.

    Now when we invoke this servlet through browser with GET method, we get response like below image. Since browser understand only HTML, when our application throw exception, servlet container processes the exception and generate a HTML response. This logic is specific to servlet container. I am using tomcat and getting this error page. If you will use some other servers like JBoss or Glassfish, you might get different error HTML response. The problem with this response is that it’s of no value to user. Also it’s showing our application classes and server details to user that makes no sense to user and it’s not good from security point of view.

    Servlet Error

    I am sure you must have seen 404 error when you are trying to hit a URL that doesn’t exists. Let’s see how our servlet container responds to 404 error. If we send request for an invalid URL, we get response HTML like below image. Again it’s a generic HTML generated by server on our application behalf and hold little to no value to the user.

    Servlet Exception and Error Handling

    Servlet API provides support for custom Exception and Error Handler servlets that we can configure in deployment descriptor. The whole purpose of these servlets are to handle the Exception or Error raised by application and send useful HTML response to user. We can provide link to application home page or some details to let user know what went wrong. So first of all we need to create a custom Exception and Error Handler servlet. We can have multiple exception and error handler servlets for the application but for simplicity I will create a single servlet and use it for both exceptions and errors. AppExceptionHandler.java

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    Let’s see how we can configure it in deployment descriptor and then we will understand it’s implementation and how it works.

    As you can see, it’s very easy to specify Exception handler servlets for the application using error-page element. Each error-page element should have either error-code or exception-type element. We define the exception handler servlet in location element. Based on above configuration, if the application throw 404 error or ServletException, it will be handled by AppExceptionHandler servlet. When such exception and error scenario appears, servlet container will invoke the corresponding HTTP method of the Exception Handler servlet and pass the request and response object. Notice that I have provided implementation of both doGet() and doPost() methods so that it can handle GET and POST requests and using a common method to process them. Before servlet container invokes the servlet to handle the exception, it sets some attributes in the request to get useful information about the exception, some of them are javax.servlet.error.exception, javax.servlet.error.status_code, javax.servlet.error.servlet_name and javax.servlet.error.request_uri. For exception, status code is always 500 that corresponds to the “Internal Server Error”, for other types of error we get different error codes such as 404, 403 etc. Using the status code, our implementation presents different types of HTML response to the user. It also provides a hyperlink to the home page of the application. Now when we will hit our servlet that is throwing ServletException, we will get a response like below image. If we try to access an invalid URL that will result in 404 response, we will get response like below image. Doesn’t it look good and helps user to easily understand what happened and provides them a way to go to the correct location. It also avoids sending application sensitive information to the user. We should always have exception handlers in place for our web application. If you want to handle runtime exceptions and all other exceptions in a single exception handler, you can provide exception-type as Throwable.

    If there are multiple error-page entries, let’s say one for Throwable and one for IOException and application throws FileNotFoundException then it will be handled by error handler of IOException. You can also use JSP page as exception handler, just provide the location of jsp file rather than servlet mapping. That’s all for servlet exception handling in web application, I hope you liked it.

    Check out other articles in this series:

    If you’ve enjoyed this tutorial and our broader community, consider checking out our DigitalOcean products which can also help you achieve your development goals.

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