Fork JsonRef for improved performance.

Pull request pending: java-json-tools/json-schema-core#24

src/main/scala/com/github/fge/jsonschema/core/ref/JsonRef.java

@@ -0,0 +1,346 @@
+/*
+ * Copyright (c) 2014, Francis Galiegue ([email protected])
+ *
+ * This software is dual-licensed under:
+ *
+ * - the Lesser General Public License (LGPL) version 3.0 or, at your option, any
+ *   later version;
+ * - the Apache Software License (ASL) version 2.0.
+ *
+ * The text of this file and of both licenses is available at the root of this
+ * project or, if you have the jar distribution, in directory META-INF/, under
+ * the names LGPL-3.0.txt and ASL-2.0.txt respectively.
+ *
+ * Direct link to the sources:
+ *
+ * - LGPL 3.0: https://www.gnu.org/licenses/lgpl-3.0.txt
+ * - ASL 2.0: http://www.apache.org/licenses/LICENSE-2.0.txt
+ */
+
+package com.github.fge.jsonschema.core.ref;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.github.fge.jackson.jsonpointer.JsonPointer;
+import com.github.fge.jackson.jsonpointer.JsonPointerException;
+import com.github.fge.jsonschema.core.exceptions.JsonReferenceException;
+import com.github.fge.jsonschema.core.exceptions.ProcessingException;
+import com.github.fge.jsonschema.core.messages.JsonSchemaCoreMessageBundle;
+import com.github.fge.jsonschema.core.report.ProcessingMessage;
+import com.github.fge.jsonschema.core.util.URIUtils;
+import com.github.fge.msgsimple.bundle.MessageBundle;
+import com.github.fge.msgsimple.load.MessageBundles;
+import com.google.common.base.Optional;
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.CacheBuilderSpec;
+import com.google.common.cache.CacheLoader;
+import com.google.common.cache.LoadingCache;
+
+import javax.annotation.Nonnull;
+import javax.annotation.concurrent.Immutable;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Representation of a JSON Reference
+ *
+ * <p><a href="http://tools.ietf.org/html/draft-pbryan-zyp-json-ref-03">JSON
+ * Reference</a>, currently a draft, is a way to define a path within a JSON
+ * document.</p>
+ *
+ * <p>To quote the draft, "A JSON Reference is a JSON object, which contains
+ * a member named "$ref", which has a JSON string value." This string value
+ * must be a URI. Example:</p>
+ *
+ * <pre>
+ *     {
+ *         "$ref": "http://example.com/example.json#/foo/bar"
+ *     }
+ * </pre>
+ *
+ * <p>This class differs from the JSON Reference draft in that it accepts to
+ * process illegal references, in the sense that they are URIs, but their
+ * fragment parts are not JSON Pointers (in which case {@link #isLegal()}
+ * returns {@code false}.</p>
+ *
+ * <p>The implementation is a wrapper over Java's {@link URI}, with the
+ * following characteristics:</p>
+ *
+ * <ul>
+ *     <li>all URIs are normalized from the get go;</li>
+ *     <li>an empty fragment is equivalent to no fragment at all, and stands for
+ *     a root JSON Pointer, as required by the draft;</li>
+ *     <li>a reference is taken to be absolute if the underlying URI is absolute
+ *     <i>and</i> it has no fragment, or an empty fragment.</li>
+ * </ul>
+ *
+ * <p>It also special cases the following:</p>
+ *
+ * <ul>
+ *     <li>an empty reference (for instance, used in anonymouns schemas);</li>
+ *     <li>URIs with the {@code jar} scheme (the resolving algorithm differs --
+ *     please note that this breaks URI resolution rules).</li>
+ * </ul>
+ *
+ */
+@Immutable
+public abstract class JsonRef
+{
+    private static final MessageBundle BUNDLE
+        = MessageBundles.getBundle(JsonSchemaCoreMessageBundle.class);
+
+    /**
+     * The empty URI
+     */
+    private static final URI EMPTY_URI = URI.create("");
+
+    /**
+     * A "hash only" URI -- used by {@link EmptyJsonRef}
+     */
+    protected static final URI HASHONLY_URI = URI.create("#");
+
+    /**
+     * Whether this JSON Reference is legal
+     */
+    protected final boolean legal;
+
+    /**
+     * The URI, as provided by the input, with an appended empty fragment if
+     * no fragment was provided
+     */
+    protected final URI uri;
+
+    /**
+     * The locator of this reference. This is the URI with an empty fragment
+     * part.
+     */
+    protected final URI locator;
+
+    /**
+     * The pointer of this reference, if any
+     *
+     * <p>Initialized to null if the fragment part is not a JSON Pointer.</p>
+     *
+     * @see #isLegal()
+     */
+    protected final JsonPointer pointer;
+
+    /**
+     * String representation
+     */
+    private final String asString;
+
+    /**
+     * Hashcode
+     */
+    private final int hashCode;
+
+    /**
+     * Main constructor, {@code protected} by design
+     *
+     * @param uri the URI to build that reference
+     */
+    protected JsonRef(final URI uri)
+    {
+        final String scheme = uri.getScheme();
+        final String ssp = uri.getSchemeSpecificPart();
+        /*
+         * Account for URIs with no fragment: substitute an empty one
+         */
+        final String fragment = Optional.fromNullable(uri.getFragment()).or("");
+
+        /*
+         * Compute the fragment
+         */
+        boolean isLegal = true;
+        JsonPointer ptr;
+        try {
+            ptr = fragment.isEmpty() ? JsonPointer.empty()
+                : new JsonPointer(fragment);
+        } catch (JsonPointerException ignored) {
+            ptr = null;
+            isLegal = false;
+        }
+        legal = isLegal;
+        pointer = ptr;
+
+        try {
+            this.uri = new URI(scheme, ssp, fragment);
+            locator = new URI(scheme, ssp, "");
+            asString = this.uri.toString();
+            hashCode = asString.hashCode();
+        } catch (URISyntaxException e) {
+            /*
+             * Can't happen: we did have a legal URI to start with
+             */
+            throw new RuntimeException("WTF??", e);
+        }
+    }
+
+    private static LoadingCache<URI, JsonRef> uriToJsonRef = CacheBuilder.newBuilder().maximumSize(1000).build(new CacheLoader<URI, JsonRef>() {
+        public JsonRef load(@Nonnull final URI uri) {
+            final URI normalized = URIUtils.normalizeURI(uri);
+            if (HASHONLY_URI.equals(normalized) || EMPTY_URI.equals(normalized)) return EmptyJsonRef.getInstance();
+            return "jar".equals(normalized.getScheme()) ? new JarJsonRef(normalized) : new HierarchicalJsonRef(normalized);
+        }
+    });
+
+    /**
+     * Build a JSON Reference from a URI
+     *
+     * @param uri the provided URI
+     * @return the JSON Reference
+     * @throws NullPointerException the provided URI is null
+     */
+    public static JsonRef fromURI(final URI uri)
+    {
+        BUNDLE.checkNotNull(uri, "jsonRef.nullURI");
+        return uriToJsonRef.getUnchecked(uri);
+    }
+
+    /**
+     * Build a JSON Reference from a string input
+     *
+     * @param s the string
+     * @return the reference
+     * @throws JsonReferenceException string is not a valid URI
+     * @throws NullPointerException provided string is null
+     */
+    public static JsonRef fromString(final String s)
+        throws JsonReferenceException
+    {
+        BUNDLE.checkNotNull(s, "jsonRef.nullInput");
+        try {
+            return fromURI(new URI(s));
+        } catch (URISyntaxException e) {
+            throw new JsonReferenceException(new ProcessingMessage()
+                .setMessage(BUNDLE.getMessage("jsonRef.invalidURI"))
+                .putArgument("input", s), e);
+        }
+
+    }
+
+    /**
+     * Return an empty reference
+     *
+     * <p>An empty reference is a reference which only has an empty fragment.
+     * </p>
+     *
+     * @return a statically allocated empty reference
+     */
+    public static JsonRef emptyRef()
+    {
+        return EmptyJsonRef.getInstance();
+    }
+
+    /**
+     * Return the underlying URI for this JSON Reference
+     *
+     * @return the URI
+     */
+    public final URI toURI()
+    {
+        return uri;
+    }
+
+    /**
+     * Tell whether this reference is an absolute reference
+     *
+     * <p>See description.</p>
+     *
+     * @return {@code true} if the JSON Reference is absolute
+     */
+    public abstract boolean isAbsolute();
+
+    /**
+     * Resolve this reference against another reference
+     *
+     * @param other the reference to resolve
+     * @return the resolved reference
+     */
+    public abstract JsonRef resolve(final JsonRef other);
+
+    /**
+     * Return this JSON Reference's locator
+     *
+     * <p>This returns the reference with an empty fragment, ie the URI of the
+     * document itself.</p>
+     *
+     * @return an URI
+     */
+    public final URI getLocator()
+    {
+        return locator;
+    }
+
+    /**
+     * Tell whether this JSON Reference is legal
+     *
+     * <p>Recall: it is legal if and only if its fragment part is a JSON
+     * pointer.</p>
+     *
+     * @return {@code true} if legal
+     * @see JsonPointer
+     */
+    public final boolean isLegal()
+    {
+        return legal;
+    }
+
+    /**
+     * Return the fragment part of this JSON Reference as a JSON Pointer
+     *
+     * <p>If the reference is not legal, this returns {@code null} <b>without
+     * further notice</b>, so beware!</p>
+     *
+     * @return a JSON Pointer
+     * @see JsonPointer
+     */
+    public final JsonPointer getPointer()
+    {
+        return pointer;
+    }
+
+    /**
+     * Tell whether the current JSON Reference "contains" another
+     *
+     * <p>This is considered true iif both references have the same locator,
+     * in other words, if they differ only by their fragment part.</p>
+     *
+     * @param other the other reference
+     * @return see above
+     */
+    public final boolean contains(final JsonRef other)
+    {
+        return locator.equals(other.locator);
+    }
+
+    @Override
+    public final int hashCode()
+    {
+        return hashCode;
+    }
+
+    @Override
+    public final boolean equals(final Object obj)
+    {
+        if (obj == null)
+            return false;
+        if (this == obj)
+            return true;
+
+        if (!(obj instanceof JsonRef))
+            return false;
+
+        final JsonRef that = (JsonRef) obj;
+        return asString.equals(that.asString);
+    }
+
+    @Override
+    public final String toString()
+    {
+        return asString;
+    }
+}