• The Jar Scanner Component

    Table of Contents

    Introduction

    The Jar Scanner element represents the component that is used to scan the web application for JAR files and directories of class files. It is typically used during web application start to identify configuration files such as TLDs or web-fragment.xml files that must be processed as part of the web application initialisation.

    A Jar Scanner element MAY be nested inside a Context component.

    For example you can include the bootstrap classpath when scanning for jar files:

    <Context>
      ...
      <JarScanner scanBootstrapClassPath="true"/>
      ...
    </Context>

    If a Jar Scanner element is not included, a default Jar Scanner configuration will be created automatically, which is sufficient for most requirements.

    Attributes

    Common Attributes

    All implementations of Jar Scanner support the following attributes:

    Attribute Description
    className

    Java class name of the implementation to use. This class must implement the org.apache.tomcat.JarScanner interface. If not specified, the standard value (defined below) will be used.

    Standard Implementation

    The standard implementation of Jar Scanner is org.apache.tomcat.util.scan.StandardJarScanner. It supports the following additional attributes (in addition to the common attributes listed above):

    Attribute Description
    scanAllDirectories

    If true, any directories found on the classpath will be checked to see if they are expanded JAR files. The default is false.

    Tomcat determines if a directory is an expanded JAR file by looking for a META-INF sub-directory. Only if the META-INF sub-directory exists, the directory is assumed to be an expanded JAR file. Note that for scans for matches to @HandlesTypes annotations, all directories will be scanned irrespective of the presence or not of a META-INF sub-directory.

    scanAllFiles

    If true, any files found on the classpath will be checked to see if they are Jar files rather than relying on the file extension being .jar. The default is false.

    scanClassPath

    If true, the full web application classpath, including the shared and common classloaders and the system classpath (but not the bootstrap classpath) will be scanned for Jar files in addition to the web application. The default is true.

    scanBootstrapClassPath

    If scanClassPath is true and this is true the bootstrap classpath will also be scanned for Jar files. The default is false.

    scanManifest

    If true, the Manifest files of any JARs found will be scanned for additional class path entries and those entries will be added to the URLs to scan. The default is true.

    Nested Components

    Only a Jar Scan Filter may be nested inside a Jar Scanner element.

    Special Features

    No special features are associated with a Jar Scanner element.

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