# Apache Tomcat 7

Version 7.0.106, Sep 16 2020

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# The Jar Scanner Component

Table of Contents

> - Introduction
> - Attributes
>   1. Common Attributes
>   2. Standard Implementation
> - Nested Components
> - Special Features

Introduction

> The Jar Scanner element represents the component that is used to scan the web application for JAR 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. If it 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. Additional attributes that it supports (in addition to the common attributes listed above) are listed in the table.

> > There are several system properties that control what JAR files are skipped by JarScanner. Those properties are lists of file name pattern. The patterns are separated by comma (','). The leading and trailing whitespace characters in a pattern are ignored. The patterns are matched case-sensitively. The following two special characters are supported:

> > - '*' — means zero or more characters,
> > - '?' — means one and only one character.

> > 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.
> > `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`.

Nested Components

> No components may be nested inside a Jar Scanner element.

Special Features

> No special features are associated with a Jar Scanner element.

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