The jar package under Myeclipse's web project lib, the solution that cannot be found in reference libraries

The specific role of .project and .classpath files in eclipse: http://www.cnblogs.com/panjun-Donet/archive/2010/08/25/1807780.html
Myeclipse project generally has the following two files:
.project is The project file and the structure of the project are defined in it, such as the location of lib, the location of src, and the location of classes. The location of
classpath defines the $CLASSPATH used by your project when compiling.
These files can be viewed with a text editor. The purpose of refreshing
in

a project is to update the file list in the .project file, allowing you to display the files that are not submitted to the project through eclipse. The classpath file

  is easy to see from the data, the above describes the dependencies of the project File:

    The specific location of the source file (kind="src")
    the system environment (kind="con") of the running system environment (kind="con")
    The specific location information of the project's library (kind="lib")
    is in the xml child node of each lib, there are Regarding its other configuration information (such as the "javadoc_location" I configured)
    , the output directory (kind="output")

of the project is generally said to configure the running environment of the entire project.

     .project file

From the data point of view, we can understand that these configurations are mainly to describe the basic information of the project:

    project name <name>
    Project comments describe <comment></comment>
    additional Eclipse plugins <natures></natures> required at runtime, and their specific loading method information <buildSpec></buildSpec>

If you add a lot to the project during the development process Additional plug-ins will inevitably cause your Eclipse to start slower. In this case, you can go to this file and remove some plugins, but then you will load those plugins when you open those associated files.

     The .settings file

     contains configuration files for various plugins.

The above is a brief introduction to the hidden configuration files related to Eclipse's Project.

My .project file:

<?xml version="1.0" encoding="UTF-8"?>
<projectDescription>
	<name>joke</name>
	<comment></comment>
	<projects>
	</projects>
	<buildSpec>
		<buildCommand>
			<name>org.eclipse.wst.jsdt.core.javascriptValidator</name>
			<arguments>
			</arguments>
		</buildCommand>
		<buildCommand>
			<name>org.eclipse.jdt.core.javabuilder</name>
			<arguments>
			</arguments>
		</buildCommand>
		<buildCommand>
			<name>org.eclipse.wst.common.project.facet.core.builder</name>
			<arguments>
			</arguments>
		</buildCommand>
		<buildCommand>
			<name>org.eclipse.wst.validation.validationbuilder</name>
			<arguments>
			</arguments>
		</buildCommand>
		<buildCommand>
			<name>com.genuitec.eclipse.j2eedt.core.DeploymentDescriptorValidator</name>
			<arguments>
			</arguments>
		</buildCommand>
		<buildCommand>
			<name>com.genuitec.eclipse.ast.deploy.core.DeploymentBuilder</name>
			<arguments>
			</arguments>
		</buildCommand>
	</buildSpec>
	<natures>
		<nature>com.genuitec.eclipse.ast.deploy.core.deploymentnature</nature>
		<nature>org.eclipse.jem.workbench.JavaEMFNature</nature>
		<nature>org.eclipse.wst.common.modulecore.ModuleCoreNature</nature>
		<nature>org.eclipse.wst.common.project.facet.core.nature</nature>
		<nature>org.eclipse.jdt.core.javanature</nature>
		<nature>org.eclipse.wst.jsdt.core.jsNature</nature>
	</natures>
</projectDescription>

My .classpath file:

<?xml version="1.0" encoding="UTF-8"?>
<classpath>
	<classpathentry kind="src" path="src"/>
	<classpathentry kind="src" path="resources"/>
	<classpathentry kind="con" path="org.eclipse.jst.j2ee.internal.module.container"/>
	<classpathentry kind="con" path="com.genuitec.runtime.library/com.genuitec.jstl_1.2.1">
		<attributes>
			<attribute name="org.eclipse.jst.component.dependency" value="WEB-INF/lib"/>
			<attribute name="owner.project.facets" value="jst.web.jstl"/>
		</attributes>
	</classpathentry>
	<classpathentry kind="lib" path="WebRoot/WEB-INF/lib/aopalliance-1.0.jar"/>
	<classpathentry kind="lib" path="WebRoot/WEB-INF/lib/poi-3.11-20141221.jar"/>
	<classpathentry kind="lib" path="WebRoot/WEB-INF/lib/poi-examples-3.11-20141221.jar"/>

	<classpathentry kind="lib" path="WebRoot/WEB-INF/lib/QRCode.jar"/>
        <classpathentry kind="lib" path="WebRoot/WEB-INF/lib/quartz-2.2.1.jar"/>
	<classpathentry kind="lib" path="WebRoot/WEB-INF/lib/sun.misc.BASE64Decoder.jar"/>
	<classpathentry kind="lib" path="WebRoot/WEB-INF/lib/ueditor.jar"/>
	<classpathentry kind="lib" path="WebRoot/WEB-INF/lib/weixinapi.jar"/>
	<classpathentry kind="lib" path="WebRoot/WEB-INF/lib/wsdl4j-1.6.3.jar"/>
	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/jre7"/>
	<classpathentry kind="output" path="WebRoot/WEB-INF/classes"/>
</classpath>

Mine is quartz-2.2.1.jar not found, in the .classpath file, add
<classpathentry kind="lib" path="WebRoot/WEB-INF/lib/quartz-2.2.1.jar"/>
and then Just refresh the project