I want to develop with Servlets in Eclipse, but it says that the package
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 Oracle.com 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?
Once having installed both Eclipse for Java EE and a servletcontainer on your machine, do the following steps in Eclipse:
Integrate servletcontainer in Eclipse
a. Via Servers view
Pick the appropriate servletcontainer make and version and walk through the wizard.
b. Or, via Eclipse preferences
Associate server with project
a. In new project
In the wizard, set the Target Runtime to the integrated server.
b. Or, in existing project
In Targeted Runtimes section, select the integrated server.
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.
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
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
Here are some typical exceptions which you can get when you litter the
/WEB-INF/lib or even
/JRE/lib/ext, etc with servletcontainer-specific libraries in a careless attempt to fix the compilation errors: