https://tomcat.apache.org/: Tomcat Servlet Engine Core Classes and Standard implementations 
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package org.apache.catalina.util;


import java.util.StringTokenizer;



Utility class that represents either an available "Optional Package"
(formerly known as "Standard Extension") as described in the manifest
of a JAR file, or the requirement for such an optional package.  It is
used to support the requirements of the Servlet Specification, version
2.3, related to providing shared extensions to all webapps.


In addition, static utility methods are available to scan a manifest
and return an array of either available or required optional modules
documented in that manifest.


For more information about optional packages, see the document
Optional Package Versioning in the documentation bundle for your
Java2 Standard Edition package, in file
guide/extensions/versioning.html.

Author:Craig McClanahan, Justyna Horwat, Greg Murray
/**
 * Utility class that represents either an available "Optional Package"
 * (formerly known as "Standard Extension") as described in the manifest
 * of a JAR file, or the requirement for such an optional package.  It is
 * used to support the requirements of the Servlet Specification, version
 * 2.3, related to providing shared extensions to all webapps.
 * <p>
 * In addition, static utility methods are available to scan a manifest
 * and return an array of either available or required optional modules
 * documented in that manifest.
 * <p>
 * For more information about optional packages, see the document
 * <em>Optional Package Versioning</em> in the documentation bundle for your
 * Java2 Standard Edition package, in file
 * <code>guide/extensions/versioning.html</code>.
 *
 * @author Craig McClanahan
 * @author Justyna Horwat
 * @author Greg Murray
 */
public final class Extension {


    // ------------------------------------------------------------- Properties


    
The name of the optional package being made available, or required.

/**
     * The name of the optional package being made available, or required.
     */
    private String extensionName = null;


    public String getExtensionName() {
        return this.extensionName;
    }

    public void setExtensionName(String extensionName) {
        this.extensionName = extensionName;
    }

    
The URL from which the most recent version of this optional package
can be obtained if it is not already installed.

/**
     * The URL from which the most recent version of this optional package
     * can be obtained if it is not already installed.
     */
    private String implementationURL = null;

    public String getImplementationURL() {
        return this.implementationURL;
    }

    public void setImplementationURL(String implementationURL) {
        this.implementationURL = implementationURL;
    }


    
The name of the company or organization that produced this
implementation of this optional package.

/**
     * The name of the company or organization that produced this
     * implementation of this optional package.
     */
    private String implementationVendor = null;

    public String getImplementationVendor() {
        return this.implementationVendor;
    }

    public void setImplementationVendor(String implementationVendor) {
        this.implementationVendor = implementationVendor;
    }


    
The unique identifier of the company that produced the optional
package contained in this JAR file.

/**
     * The unique identifier of the company that produced the optional
     * package contained in this JAR file.
     */
    private String implementationVendorId = null;

    public String getImplementationVendorId() {
        return this.implementationVendorId;
    }

    public void setImplementationVendorId(String implementationVendorId) {
        this.implementationVendorId = implementationVendorId;
    }


    
The version number (dotted decimal notation) for this implementation
of the optional package.

/**
     * The version number (dotted decimal notation) for this implementation
     * of the optional package.
     */
    private String implementationVersion = null;

    public String getImplementationVersion() {
        return this.implementationVersion;
    }

    public void setImplementationVersion(String implementationVersion) {
        this.implementationVersion = implementationVersion;
    }


    
The name of the company or organization that originated the
specification to which this optional package conforms.

/**
     * The name of the company or organization that originated the
     * specification to which this optional package conforms.
     */
    private String specificationVendor = null;

    public String getSpecificationVendor() {
        return this.specificationVendor;
    }

    public void setSpecificationVendor(String specificationVendor) {
        this.specificationVendor = specificationVendor;
    }


    
The version number (dotted decimal notation) of the specification
to which this optional package conforms.

/**
     * The version number (dotted decimal notation) of the specification
     * to which this optional package conforms.
     */
    private String specificationVersion = null;

    public String getSpecificationVersion() {
        return this.specificationVersion;
    }

    public void setSpecificationVersion(String specificationVersion) {
        this.specificationVersion = specificationVersion;
    }


    
fulfilled is true if all the required extension dependencies have been
satisfied

/**
     * fulfilled is true if all the required extension dependencies have been
     * satisfied
     */
    private boolean fulfilled = false;

    public void setFulfilled(boolean fulfilled) {
        this.fulfilled = fulfilled;
    }

    public boolean isFulfilled() {
        return fulfilled;
    }

    // --------------------------------------------------------- Public Methods

    
Return true if the specified Extension
(which represents an optional package required by this application)
is satisfied by this Extension (which represents an
optional package that is already installed.  Otherwise, return
false.

Params:
  • required – Extension of the required optional package
Returns:true if the extension is satisfied
/**
     * Return <code>true</code> if the specified <code>Extension</code>
     * (which represents an optional package required by this application)
     * is satisfied by this <code>Extension</code> (which represents an
     * optional package that is already installed.  Otherwise, return
     * <code>false</code>.
     *
     * @param required Extension of the required optional package
     * @return <code>true</code> if the extension is satisfied
     */
    public boolean isCompatibleWith(Extension required) {

        // Extension Name must match
        if (extensionName == null)
            return false;
        if (!extensionName.equals(required.getExtensionName()))
            return false;

        // If specified, available specification version must be >= required
        if (required.getSpecificationVersion() != null) {
            if (!isNewer(specificationVersion,
                         required.getSpecificationVersion()))
                return false;
        }

        // If specified, Implementation Vendor ID must match
        if (required.getImplementationVendorId() != null) {
            if (implementationVendorId == null)
                return false;
            if (!implementationVendorId.equals(required
                    .getImplementationVendorId()))
                return false;
        }

        // If specified, Implementation version must be >= required
        if (required.getImplementationVersion() != null) {
            if (!isNewer(implementationVersion,
                         required.getImplementationVersion()))
                return false;
        }

        // This available optional package satisfies the requirements
        return true;

    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder("Extension[");
        sb.append(extensionName);
        if (implementationURL != null) {
            sb.append(", implementationURL=");
            sb.append(implementationURL);
        }
        if (implementationVendor != null) {
            sb.append(", implementationVendor=");
            sb.append(implementationVendor);
        }
        if (implementationVendorId != null) {
            sb.append(", implementationVendorId=");
            sb.append(implementationVendorId);
        }
        if (implementationVersion != null) {
            sb.append(", implementationVersion=");
            sb.append(implementationVersion);
        }
        if (specificationVendor != null) {
            sb.append(", specificationVendor=");
            sb.append(specificationVendor);
        }
        if (specificationVersion != null) {
            sb.append(", specificationVersion=");
            sb.append(specificationVersion);
        }
        sb.append(']');
        return sb.toString();
    }


    // -------------------------------------------------------- Private Methods



    
Return true if the first version number is greater than
or equal to the second; otherwise return false.

Params:
  • first – First version number (dotted decimal)
  • second – Second version number (dotted decimal)
Throws:
/**
     * Return <code>true</code> if the first version number is greater than
     * or equal to the second; otherwise return <code>false</code>.
     *
     * @param first First version number (dotted decimal)
     * @param second Second version number (dotted decimal)
     *
     * @exception NumberFormatException on a malformed version number
     */
    private boolean isNewer(String first, String second)
        throws NumberFormatException {

        if ((first == null) || (second == null))
            return false;
        if (first.equals(second))
            return true;

        StringTokenizer fTok = new StringTokenizer(first, ".", true);
        StringTokenizer sTok = new StringTokenizer(second, ".", true);
        int fVersion = 0;
        int sVersion = 0;
        while (fTok.hasMoreTokens() || sTok.hasMoreTokens()) {
            if (fTok.hasMoreTokens())
                fVersion = Integer.parseInt(fTok.nextToken());
            else
                fVersion = 0;
            if (sTok.hasMoreTokens())
                sVersion = Integer.parseInt(sTok.nextToken());
            else
                sVersion = 0;
            if (fVersion < sVersion)
                return false;
            else if (fVersion > sVersion)
                return true;
            if (fTok.hasMoreTokens())   // Swallow the periods
                fTok.nextToken();
            if (sTok.hasMoreTokens())
                sTok.nextToken();
        }

        return true;  // Exact match

    }


}