#62 - Added support for application/vnd.error+(json|xml).

Introduced representation models for the application/vnd.error media type as specified in [0]. Added default mapping annotations to get it rendered in XML (via JAXB), and JSON (via Jackson 1 and 2).

[0] https://github.com/blongden/vnd.error

src/main/java/org/springframework/hateoas/VndErrors.java

@@ -0,0 +1,170 @@
+/*
+ * Copyright 2013 the original author or authors.
+ *
+ * Licensed 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.springframework.hateoas;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+
+import javax.xml.bind.annotation.XmlAttribute;
+import javax.xml.bind.annotation.XmlElement;
+import javax.xml.bind.annotation.XmlRootElement;
+import javax.xml.bind.annotation.XmlType;
+
+import org.springframework.util.Assert;
+
+import com.fasterxml.jackson.annotation.JsonValue;
+
+/**
+ * A representation model class to be rendered as specified for the media type {@code application/vnd.error}.
+ * 
+ * @see https://github.com/blongden/vnd.error
+ * @author Oliver Gierke
+ */
+@XmlRootElement(name = "errors")
+public class VndErrors implements Iterable<VndErrors.VndError> {
+
+	@XmlElement(name = "error")
+	private final List<VndError> vndErrors;
+
+	/**
+	 * Creates a new {@link VndErrors} instance containing a single {@link VndError} with the given logref, message and
+	 * optional {@link Link}s.
+	 * 
+	 * @param logref must not be {@literal null} or empty.
+	 * @param message must not be {@literal null} or empty.
+	 * @param links
+	 */
+	public VndErrors(String logref, String message, Link... links) {
+		this(new VndError(logref, message, links));
+	}
+
+	/**
+	 * Creates a new {@link VndErrors} wrapper for at least one {@link VndError}.
+	 * 
+	 * @param errors must not be {@literal null}.
+	 * @param errors
+	 */
+	public VndErrors(VndError error, VndError... errors) {
+
+		Assert.notNull(error, "Error must not be null");
+
+		this.vndErrors = new ArrayList<VndError>(errors.length + 1);
+		this.vndErrors.add(error);
+		this.vndErrors.addAll(Arrays.asList(errors));
+	}
+
+	/**
+	 * Protected default constructor to allow JAXB marshalling.
+	 */
+	protected VndErrors() {
+		this.vndErrors = new ArrayList<VndError>();
+	}
+
+	/**
+	 * Adds an additional {@link VndError} to the wrapper.
+	 * 
+	 * @param errors
+	 */
+	public VndErrors add(VndError error) {
+		this.vndErrors.add(error);
+		return this;
+	}
+
+	/**
+	 * Dummy method to allow {@link JsonValue} to be configured.
+	 * 
+	 * @return the vndErrors
+	 */
+	@com.fasterxml.jackson.annotation.JsonValue
+	@org.codehaus.jackson.annotate.JsonValue
+	private List<VndError> getErrors() {
+		return vndErrors;
+	}
+
+	/* 
+	 * (non-Javadoc)
+	 * @see java.lang.Iterable#iterator()
+	 */
+	@Override
+	public Iterator<VndErrors.VndError> iterator() {
+		return this.vndErrors.iterator();
+	}
+
+	/**
+	 * A single {@link VndError}.
+	 * 
+	 * @author Oliver Gierke
+	 */
+	@XmlType
+	public static class VndError extends ResourceSupport {
+
+		@com.fasterxml.jackson.annotation.JsonProperty
+		@org.codehaus.jackson.annotate.JsonProperty
+		@XmlAttribute
+		private final String logref;
+
+		@com.fasterxml.jackson.annotation.JsonProperty
+		@org.codehaus.jackson.annotate.JsonProperty
+		@XmlElement
+		private final String message;
+
+		/**
+		 * Creates a new {@link VndError} with the given logref, a message as well as some {@link Link}s.
+		 * 
+		 * @param logref must not be {@literal null} or empty.
+		 * @param message must not be {@literal null} or empty.
+		 * @param links
+		 */
+		public VndError(String logref, String message, Link... links) {
+
+			Assert.hasText(logref, "Logref must not be null or empty!");
+			Assert.hasText(message, "Message must not be null or empty!");
+
+			this.logref = logref;
+			this.message = message;
+			this.add(Arrays.asList(links));
+		}
+
+		/**
+		 * Protected default constructor to allow JAXB marshalling.
+		 */
+		protected VndError() {
+
+			this.logref = null;
+			this.message = null;
+		}
+
+		/**
+		 * Returns the logref of the error.
+		 * 
+		 * @return the logref
+		 */
+		public String getLogref() {
+			return logref;
+		}
+
+		/**
+		 * Returns the message of the error.
+		 * 
+		 * @return the message
+		 */
+		public String getMessage() {
+			return message;
+		}
+	}
+}

src/test/java/org/springframework/hateoas/VndErrorsMarshallingTests.java

@@ -0,0 +1,114 @@
+/*
+ * Copyright 2013 the original author or authors.
+ *
+ * Licensed 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.springframework.hateoas;
+
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.*;
+
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.StringWriter;
+import java.io.Writer;
+import java.nio.MappedByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.charset.Charset;
+
+import javax.xml.bind.JAXBContext;
+import javax.xml.bind.Marshaller;
+
+import org.codehaus.jackson.map.ObjectMapper;
+import org.codehaus.jackson.map.SerializationConfig.Feature;
+import org.junit.Before;
+import org.junit.Test;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.hateoas.VndErrors.VndError;
+import org.springframework.hateoas.hal.Jackson1HalModule;
+import org.springframework.hateoas.hal.Jackson2HalModule;
+
+import com.fasterxml.jackson.databind.SerializationFeature;
+
+/**
+ * Integration tests for marshalling of {@link VndErrors}.
+ * 
+ * @author Oliver Gierke
+ */
+public class VndErrorsMarshallingTests {
+
+	ObjectMapper jackson1Mapper;
+	com.fasterxml.jackson.databind.ObjectMapper jackson2Mapper;
+	Marshaller marshaller;
+
+	VndErrors errors;
+	String jsonReference;
+	String xmlReference;
+
+	public VndErrorsMarshallingTests() throws IOException {
+
+		jsonReference = readFile(new ClassPathResource("vnderror.json"));
+		xmlReference = readFile(new ClassPathResource("vnderror.xml"));
+	}
+
+	@Before
+	public void setUp() throws Exception {
+
+		jackson1Mapper = new ObjectMapper();
+		jackson1Mapper.registerModule(new Jackson1HalModule());
+		jackson1Mapper.configure(Feature.INDENT_OUTPUT, true);
+
+		jackson2Mapper = new com.fasterxml.jackson.databind.ObjectMapper();
+		jackson2Mapper.registerModule(new Jackson2HalModule());
+		jackson2Mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
+
+		JAXBContext context = JAXBContext.newInstance(VndErrors.class);
+		marshaller = context.createMarshaller();
+		marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
+
+		VndError error = new VndError("42", "Validation failed!", //
+				new Link("http://...", "help"), new Link("http://...", "describes"));
+		errors = new VndErrors(error, error, error);
+	}
+
+	@Test
+	public void jackson1Marshalling() throws Exception {
+		assertThat(jackson1Mapper.writeValueAsString(errors), is(jsonReference));
+	}
+
+	@Test
+	public void jackson2Marshalling() throws Exception {
+		assertThat(jackson2Mapper.writeValueAsString(errors), is(jsonReference));
+	}
+
+	@Test
+	public void jaxbMarshalling() throws Exception {
+
+		Writer writer = new StringWriter();
+		marshaller.marshal(errors, writer);
+		assertThat(writer.toString(), is(xmlReference));
+	}
+
+	private static String readFile(org.springframework.core.io.Resource resource) throws IOException {
+
+		FileInputStream stream = new FileInputStream(resource.getFile());
+
+		try {
+			FileChannel fc = stream.getChannel();
+			MappedByteBuffer bb = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size());
+			return Charset.defaultCharset().decode(bb).toString();
+		} finally {
+			stream.close();
+		}
+	}
+}

src/test/resources/vnderror.json

@@ -0,0 +1,34 @@
+[ {
+  "logref" : "42",
+  "message" : "Validation failed!",
+  "_links" : {
+    "describes" : {
+      "href" : "http://..."
+    },
+    "help" : {
+      "href" : "http://..."
+    }
+  }
+}, {
+  "logref" : "42",
+  "message" : "Validation failed!",
+  "_links" : {
+    "describes" : {
+      "href" : "http://..."
+    },
+    "help" : {
+      "href" : "http://..."
+    }
+  }
+}, {
+  "logref" : "42",
+  "message" : "Validation failed!",
+  "_links" : {
+    "describes" : {
+      "href" : "http://..."
+    },
+    "help" : {
+      "href" : "http://..."
+    }
+  }
+} ]

src/test/resources/vnderror.xml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<errors xmlns:ns2="http://www.w3.org/2005/Atom">
+    <error logref="42">
+        <ns2:link href="http://..." rel="help"/>
+        <ns2:link href="http://..." rel="describes"/>
+        <message>Validation failed!</message>
+    </error>
+    <error logref="42">
+        <ns2:link href="http://..." rel="help"/>
+        <ns2:link href="http://..." rel="describes"/>
+        <message>Validation failed!</message>
+    </error>
+    <error logref="42">
+        <ns2:link href="http://..." rel="help"/>
+        <ns2:link href="http://..." rel="describes"/>
+        <message>Validation failed!</message>
+    </error>
+</errors>