。在写程序的时候，我反正是经常遇到某一个类声明不知道是哪一个jar包的，比如某一个开源包报告了
java.lang.NoClassDefFoundError: javax/servlet/http/HttpSessionListener
错误，搞得满世界找。
有了jarhoo好点，它声称“Searches for jar files or fully qualified java classnames usually performed under 2 seconds. Package or non-qualified classname searches may take around 10 seconds ”，只要你将javax.servlet.http.HttpSessionListener输入搜索框，他就会帮你找到各种各样的jar包，如：
The results for the Java classname of javax.servlet.http.HttpSessionListener are:
| Class Name | Jar File Name | Application Name |
|---|---|---|
| javax.servlet.http.HttpSessionListener | geronimo-spec-servlet-2.4-rc4.jar | Ibiblio Maven Repository |
| javax.servlet.http.HttpSessionListener | geronimo-spec-j2ee-1.4-rc3.jar | Ibiblio Maven Repository |
| javax.servlet.http.HttpSessionListener | servletapi-2.4.public_draft.jar | Ibiblio Maven Repository |
| javax.servlet.http.HttpSessionListener | servlet.jar | Acegi Security 0.6 for Spring Framework (with dependencies) |
| javax.servlet.http.HttpSessionListener | servlet.jar | Eclipse SDK 3.0.1 |
| javax.servlet.http.HttpSessionListener | servlet.jar | JBoss 3.2.5 |
| javax.servlet.http.HttpSessionListener | servlet.jar | JBuilder 2005 Enterprise |
| javax.servlet.http.HttpSessionListener | servlet.jar | Spring Framework 1.1 (With Dependencies) |
| javax.servlet.http.HttpSessionListener | servlet.jar | WebWork 2.1.6 |
| javax.servlet.http.HttpSessionListener | servlet.jar | XOM 1.0b6 |
| javax.servlet.http.HttpSessionListener | servlet-api-2.3.jar | Ibiblio Maven Repository |
| javax.servlet.http.HttpSessionListener | servletapi-2.4-20030804.000000.jar | Ibiblio Maven Repository |
| javax.servlet.http.HttpSessionListener | geronimo-spec-servlet-2.4-rc2.jar | Ibiblio Maven Repository |
| javax.servlet.http.HttpSessionListener | j2ee.jar | J2EE 1.4 SDK and Sun Java System Application Server Platform Edition 8 Update 1 |
| javax.servlet.http.HttpSessionListener | j2ee.jar | Websphere Application Server v5.1 Trial |
| javax.servlet.http.HttpSessionListener | servletapi-2.4-20040521.jar | Ibiblio Maven Repository |
| javax.servlet.http.HttpSessionListener | geronimo-spec-j2ee-1.0-M1.jar | Ibiblio Maven Repository |
| javax.servlet.http.HttpSessionListener | geronimo-spec-servlet-2.4-rc3.jar | Ibiblio Maven Repository |
| javax.servlet.http.HttpSessionListener | servlet-api.jar | JBoss 3.2.5 |