i resolved the problem by using the version 7.0.0pre2
of jetty-maven-plugin
and jsp-2.1
as follow :
<properties>
<jetty.version>7.0.0pre2</jetty.version>
</properties>
<dependencies>
<dependency>
<groupId>org.mortbay.jetty</groupId>
<artifactId>jsp-2.1</artifactId>
<version>${jetty.version}</version>
</dependency>
</dependencies>
<build>
<finalName>${project.artifactId}</finalName>
<plugins>
<plugin>
<groupId>org.mortbay.jetty</groupId>
<artifactId>maven-jetty-plugin</artifactId>
<version>${jetty.version}</version>
........