fn:length is undefined on all my pages now, jstl

For some reason I am getting the error below now when I do a maven install in the target folder. Why would this error happen?

The function fn:length is undefined

${fn:length(model.action.websites) <= 0}

<dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.1</version>
            <scope>provided</scope>
        </dependency>
        <开发者_开发问答;dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>

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Finally got it working. After two hours of cleaning, compiling, mvn cleaning and installing it finally broke through. I am so glad I am a .NET developer.