Mercurial > dive4elements > framework
diff artifact-database/src/main/java/org/dive4elements/artifactdatabase/ProxyArtifact.java @ 473:d0ac790a6c89 dive4elements-move
Moved directories to org.dive4elements
author | Sascha L. Teichmann <teichmann@intevation.de> |
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date | Thu, 25 Apr 2013 10:57:18 +0200 |
parents | artifact-database/src/main/java/de/intevation/artifactdatabase/ProxyArtifact.java@933bbc9fc11f |
children | 415df0fc4fa1 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/artifact-database/src/main/java/org/dive4elements/artifactdatabase/ProxyArtifact.java Thu Apr 25 10:57:18 2013 +0200 @@ -0,0 +1,186 @@ +/* + * Copyright (c) 2010 by Intevation GmbH + * + * This program is free software under the LGPL (>=v2.1) + * Read the file LGPL.txt coming with the software for details + * or visit http://www.gnu.org/licenses/ if it does not exist. + */ + +package de.intevation.artifactdatabase; + +import de.intevation.artifacts.Artifact; +import de.intevation.artifacts.CallContext; + +import java.io.IOException; +import java.io.OutputStream; + +import org.apache.log4j.Logger; + +import org.w3c.dom.Document; + +/** + * The proxy artifact is a wrapper around another artifact. It simply forwards + * the interface calls to this underlaying artifact. + * The reason for using proxy artifacts is enable the workflow to exchange + * artifacts at any time by something else without losing the concrete + * artifact. From the outside it always looks like there is only one + * distinct artifact.<br> + * + * An inner artifact is able to replace itself by indirectly hand over + * the replacement via the call context to the proxy artifact.<br> + * To do so the proxied artifact has to call + * <code>callContext.getContextValue(EPLACE_PROXY, replacement);</code>. + * After the current call (describe, feed, advance and out) of the proxied + * artifact is finished the proxy artifact replaces the former proxied artifact + * with the replacement. + * + * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a> + */ +public class ProxyArtifact +extends DefaultArtifact +{ + /** + * Key to signal that the proxied artifact should be replaced. + */ + public static final Object REPLACE_PROXY = new Object(); + + private static Logger logger = Logger.getLogger(ProxyArtifact.class); + + /** + * The proxied artifact. + */ + protected Artifact proxied; + + /** + * Default constructor. + */ + public ProxyArtifact() { + } + + /** + * Constructor to create a new proxy artifact around a given artifact. + * @param proxied The artifact to be proxied. + */ + public ProxyArtifact(Artifact proxied) { + this.proxied = proxied; + } + + /** + * The currently proxied artifact. + * @return The proxied artifact. + */ + public Artifact getProxied() { + return proxied; + } + + /** + * Explicitly set the proxied artifacts. + * @param proxied + */ + public void setProxied(Artifact proxied) { + this.proxied = proxied; + } + + @Override + public void setIdentifier(String identifier) { + this.identifier = identifier; + + if (proxied != null) + proxied.setIdentifier(identifier); + } + + /** + * Method to check if the current proxied artifact should be replaced + * by a new one coming from the call context. + * @param callContext + */ + protected void checkReplacement(CallContext callContext) { + Object replacement = callContext.getContextValue(REPLACE_PROXY); + if (replacement instanceof Artifact) { + setProxied((Artifact)replacement); + } + } + + @Override + public String hash() { + return proxied != null + ? proxied.hash() + : super.hash(); + } + + @Override + public Document describe(Document data, CallContext context) { + try { + return proxied != null + ? proxied.describe(data, context) + : super.describe(data, context); + } + finally { + checkReplacement(context); + } + } + + @Override + public Document advance(Document target, CallContext context) { + try { + return proxied != null + ? proxied.advance(target, context) + : super.advance(target, context); + } + finally { + checkReplacement(context); + } + } + + @Override + public Document feed(Document target, CallContext context) { + try { + return proxied != null + ? proxied.feed(target, context) + : super.feed(target, context); + } + finally { + checkReplacement(context); + } + } + + @Override + public void out( + Document format, + OutputStream out, + CallContext context + ) + throws IOException + { + try { + if (proxied != null) { + proxied.out(format, out, context); + } + else { + super.out(format, out, context); + } + } + finally { + checkReplacement(context); + } + } + + @Override + public void endOfLife(Object context) { + if (proxied != null) { + proxied.endOfLife(context); + } + else { + super.endOfLife(context); + } + } + + @Override + public void cleanup(Object context) { + if (proxied != null) + proxied.cleanup(context); + else + super.cleanup(context); + } +} +// vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :