extension.java

java ant的源码！非常值得看的源码

        if (null != implementationVersion) {
            try {
                this.implementationVersion
                    = new DeweyDecimal(implementationVersion);
            } catch (final NumberFormatException nfe) {
                final String error = "Bad implementation version format '"
                    + implementationVersion + "' in '" + extensionName
                    + "'. (Reason: " + nfe + ")";
                throw new IllegalArgumentException(error);
            }
        }

        if (null == this.extensionName) {
            throw new NullPointerException("extensionName property is null");
        }
    }

    /**
     * Get the name of the extension.
     *
     * @return the name of the extension
     */
    public String getExtensionName() {
        return extensionName;
    }

    /**
     * Get the vendor of the extensions specification.
     *
     * @return the vendor of the extensions specification.
     */
    public String getSpecificationVendor() {
        return specificationVendor;
    }

    /**
     * Get the version of the extensions specification.
     *
     * @return the version of the extensions specification.
     */
    public DeweyDecimal getSpecificationVersion() {
        return specificationVersion;
    }

    /**
     * Get the url of the extensions implementation.
     *
     * @return the url of the extensions implementation.
     */
    public String getImplementationURL() {
        return implementationURL;
    }

    /**
     * Get the vendor of the extensions implementation.
     *
     * @return the vendor of the extensions implementation.
     */
    public String getImplementationVendor() {
        return implementationVendor;
    }

    /**
     * Get the vendorID of the extensions implementation.
     *
     * @return the vendorID of the extensions implementation.
     */
    public String getImplementationVendorID() {
        return implementationVendorID;
    }

    /**
     * Get the version of the extensions implementation.
     *
     * @return the version of the extensions implementation.
     */
    public DeweyDecimal getImplementationVersion() {
        return implementationVersion;
    }

    /**
     * Return a Compatibility enum indicating the relationship of this
     * <code>Extension</code> with the specified <code>Extension</code>.
     *
     * @param required Description of the required optional package
     * @return the enum indicating the compatibility (or lack thereof)
     *         of specifed extension
     */
    public Compatibility getCompatibilityWith(final Extension required) {
        // Extension Name must match
        if (!extensionName.equals(required.getExtensionName())) {
            return INCOMPATIBLE;
        }

        // Available specification version must be >= required
        final DeweyDecimal requiredSpecificationVersion
            = required.getSpecificationVersion();
        if (null != requiredSpecificationVersion) {
            if (null == specificationVersion
                || !isCompatible(specificationVersion, requiredSpecificationVersion)) {
                return REQUIRE_SPECIFICATION_UPGRADE;
            }
        }

        // Implementation Vendor ID must match
        final String requiredImplementationVendorID
            = required.getImplementationVendorID();
        if (null != requiredImplementationVendorID) {
            if (null == implementationVendorID
                || !implementationVendorID.equals(requiredImplementationVendorID)) {
                return REQUIRE_VENDOR_SWITCH;
            }
        }

        // Implementation version must be >= required
        final DeweyDecimal requiredImplementationVersion
            = required.getImplementationVersion();
        if (null != requiredImplementationVersion) {
            if (null == implementationVersion
                || !isCompatible(implementationVersion, requiredImplementationVersion)) {
                return REQUIRE_IMPLEMENTATION_UPGRADE;
            }
        }

        // This available optional package satisfies the requirements
        return COMPATIBLE;
    }

    /**
     * Return <code>true</code> if the specified <code>Extension</code>
     * (which represents an optional package required by an application)
     * is satisfied by this <code>Extension</code> (which represents an
     * optional package that is already installed.  Otherwise, return
     * <code>false</code>.
     *
     * @param required Description of the required optional package
     * @return true if the specified extension is compatible with this extension
     */
    public boolean isCompatibleWith(final Extension required) {
        return (COMPATIBLE == getCompatibilityWith(required));
    }

    /**
     * Return a String representation of this object.
     *
     * @return string representation of object.
     */
    public String toString() {
        final String brace = ": ";

        final StringBuffer sb = new StringBuffer(EXTENSION_NAME.toString());
        sb.append(brace);
        sb.append(extensionName);
        sb.append(StringUtils.LINE_SEP);

        if (null != specificationVersion) {
            sb.append(SPECIFICATION_VERSION);
            sb.append(brace);
            sb.append(specificationVersion);
            sb.append(StringUtils.LINE_SEP);
        }

        if (null != specificationVendor) {
            sb.append(SPECIFICATION_VENDOR);
            sb.append(brace);
            sb.append(specificationVendor);
            sb.append(StringUtils.LINE_SEP);
        }

        if (null != implementationVersion) {
            sb.append(IMPLEMENTATION_VERSION);
            sb.append(brace);
            sb.append(implementationVersion);
            sb.append(StringUtils.LINE_SEP);
        }

        if (null != implementationVendorID) {
            sb.append(IMPLEMENTATION_VENDOR_ID);
            sb.append(brace);
            sb.append(implementationVendorID);
            sb.append(StringUtils.LINE_SEP);
        }

        if (null != implementationVendor) {
            sb.append(IMPLEMENTATION_VENDOR);
            sb.append(brace);
            sb.append(implementationVendor);
            sb.append(StringUtils.LINE_SEP);
        }

        if (null != implementationURL) {
            sb.append(IMPLEMENTATION_URL);
            sb.append(brace);
            sb.append(implementationURL);
            sb.append(StringUtils.LINE_SEP);
        }

        return sb.toString();
    }

    /**
     * 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)
     */
    private boolean isCompatible(final DeweyDecimal first,
                                 final DeweyDecimal second) {
        return first.isGreaterThanOrEqual(second);
    }

    /**
     * Retrieve all the extensions listed under a particular key
     * (Usually EXTENSION_LIST or OPTIONAL_EXTENSION_LIST).
     *
     * @param manifest the manifest to extract extensions from
     * @param listKey the key used to get list (Usually
     *        EXTENSION_LIST or OPTIONAL_EXTENSION_LIST)
     * @return the list of listed extensions
     */
    private static Extension[] getListed(final Manifest manifest,
                                          final Attributes.Name listKey) {
        final ArrayList results = new ArrayList();
        final Attributes mainAttributes = manifest.getMainAttributes();

        if (null != mainAttributes) {
            getExtension(mainAttributes, results, listKey);
        }

        final Map entries = manifest.getEntries();
        final Iterator keys = entries.keySet().iterator();
        while (keys.hasNext()) {
            final String key = (String) keys.next();
            final Attributes attributes = (Attributes) entries.get(key);
            getExtension(attributes, results, listKey);
        }

        return (Extension[]) results.toArray(new Extension[results.size()]);
    }

    /**
     * Add required optional packages defined in the specified
     * attributes entry, if any.
     *
     * @param attributes Attributes to be parsed
     * @param required list to add required optional packages to
     * @param listKey the key to use to lookup list, usually EXTENSION_LIST
     *    or OPTIONAL_EXTENSION_LIST
     */
    private static void getExtension(final Attributes attributes,
                                     final ArrayList required,
                                     final Attributes.Name listKey) {
        final String names = attributes.getValue(listKey);
        if (null == names) {
            return;
        }

        final String[] extentions = split(names, " ");
        for (int i = 0; i < extentions.length; i++) {
            final String prefix = extentions[ i ] + "-";
            final Extension extension = getExtension(prefix, attributes);

            if (null != extension) {
                required.add(extension);
            }
        }
    }

    /**
     * Splits the string on every token into an array of strings.
     *
     * @param string the string
     * @param onToken the token
     * @return the resultant array
     */
    private static String[] split(final String string,
                                        final String onToken) {
        final StringTokenizer tokenizer = new StringTokenizer(string, onToken);
        final String[] result = new String[ tokenizer.countTokens() ];

        for (int i = 0; i < result.length; i++) {
            result[ i ] = tokenizer.nextToken();
        }

        return result;
    }

    /**
     * Extract an Extension from Attributes.
     * Prefix indicates the prefix checked for each string.
     * Usually the prefix is <em>"&lt;extension&gt;-"</em> if looking for a
     * <b>Required</b> extension. If you are looking for an
     * <b>Available</b> extension
     * then the prefix is <em>""</em>.
     *
     * @param prefix the prefix for each attribute name
     * @param attributes Attributes to searched
     * @return the new Extension object, or null
     */
    private static Extension getExtension(final String prefix,
                                          final Attributes attributes) {
        //WARNING: We trim the values of all the attributes because
        //Some extension declarations are badly defined (ie have spaces
        //after version or vendorID)
        final String nameKey = prefix + EXTENSION_NAME;
        final String name = getTrimmedString(attributes.getValue(nameKey));
        if (null == name) {
            return null;
        }

        final String specVendorKey = prefix + SPECIFICATION_VENDOR;
        final String specVendor
            = getTrimmedString(attributes.getValue(specVendorKey));
        final String specVersionKey = prefix + SPECIFICATION_VERSION;
        final String specVersion
            = getTrimmedString(attributes.getValue(specVersionKey));

        final String impVersionKey = prefix + IMPLEMENTATION_VERSION;
        final String impVersion
            = getTrimmedString(attributes.getValue(impVersionKey));
        final String impVendorKey = prefix + IMPLEMENTATION_VENDOR;
        final String impVendor
            = getTrimmedString(attributes.getValue(impVendorKey));
        final String impVendorIDKey = prefix + IMPLEMENTATION_VENDOR_ID;
        final String impVendorId
            = getTrimmedString(attributes.getValue(impVendorIDKey));
        final String impURLKey = prefix + IMPLEMENTATION_URL;
        final String impURL = getTrimmedString(attributes.getValue(impURLKey));

        return new Extension(name, specVersion, specVendor, impVersion,
                              impVendor, impVendorId, impURL);
    }

    /**
     * Trim the supplied string if the string is non-null
     *
     * @param value the string to trim or null
     * @return the trimmed string or null
     */
    private static String getTrimmedString(final String value) {
        return null == value ? null : value.trim();
    }
}