tom tom - 2 months ago 11x
Java Question

How do I import the javax.servlet API in my Eclipse project?

I want to develop with Servlets in Eclipse, but it says that the package

cannot be resolved. How can I add
package to my Eclipse project?


Ensure you've the right Eclipse and Server

Ensure that you're using at least Eclipse IDE for Java EE developers (with the EE). It contains development tools to create dynamic web projects and easily integrate servletcontainers (those tools are part of Web Tools Platform, WTP). In case you already had Eclipse IDE for Java (without EE), and manually installed some EE related plugins, then chances are that it wasn't done properly. You'd best trash it and grab the real Eclipse IDE for Java EE one.

You also need to ensure that you already have a servletcontainer installed on your machine which implements at least the same Servlet API version as the servletcontainer in the production environment, for example Apache Tomcat, Oracle GlassFish, JBoss AS/WildFly, etc. Usually, just downloading the ZIP file and extracting it is sufficient. In case of Tomcat, do not download the EXE format, that's only for Windows based production environments. See also a.o. Several ports (8005, 8080, 8009) required by Tomcat Server at localhost are already in use.

A servletcontainer is a concrete implementation of the Servlet API. Note that the Java EE SDK download at basically contains GlassFish. So if you happen to already have downloaded Java EE SDK, then you basically already have GlassFish. Also note that for example GlassFish and JBoss AS/WildFly are more than just a servletcontainer, they also supports JSF, EJB, JPA and all other Java EE fanciness. See also a.o. What exactly is Java EE?

Integrate Server in Eclipse and associate it with Project

Once having installed both Eclipse for Java EE and a servletcontainer on your machine, do the following steps in Eclipse:

  1. Integrate servletcontainer in Eclipse

    a. Via Servers view

    • Open the Servers view in the bottom box.
    • Rightclick there and choose New > Server.
    • Pick the appropriate servletcontainer make and version and walk through the wizard.

      enter image description here

    b. Or, via Eclipse preferences

    • Open Window > Preferences > Server > Runtime Environments.
    • You can Add, Edit and Remove servers here.

      enter image description here

  2. Associate server with project

    a. In new project

    • Open the Project Navigator/Explorer on the left hand side.
    • Rightclick there and choose New > Project and then in menu Web > Dynamic Web Project.
    • In the wizard, set the Target Runtime to the integrated server.

      enter image description here

    b. Or, in existing project

    • Rightclick project and choose Properties.
    • In Targeted Runtimes section, select the integrated server.

      enter image description here

    Either way, Eclipse will then automatically take the servletcontainer's libraries in the build path. This way you'll be able to import and use the Servlet API.

Never carry around loose server-specific JAR files

You should in any case not have the need to fiddle around in the Build Path property of the project. You should above all never manually copy/download/move/include the individual servletcontainer-specific libraries like servlet-api.jar, jsp-api.jar, el-api.jar, j2ee.jar, javaee.jar, etc. It would only lead to future portability, compatibility, classpath and maintainability troubles, because your webapp would not work when it's deployed to a servletcontainer of a different make/version than where those libraries are originally obtained from.

In case you're using Maven, you need to make absolutely sure that servletcontainer-specific libraries which are already provided by the target runtime are marked as <scope>provided</scope>.

Here are some typical exceptions which you can get when you litter the /WEB-INF/lib or even /JRE/lib, /JRE/lib/ext, etc with servletcontainer-specific libraries in a careless attempt to fix the compilation errors: