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#31 - Introduced LinkDiscoverer to extract Link instances from representations.

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LinkDiscoverer exposes an API to find Links by their relation types in representations. Added JSONPath based base class and a DefaultLinkDiscoverer that finds Links based on the default rendering of our Jackson mappings.
This commit is contained in:
Oliver Gierke
2012-12-15 18:29:26 +01:00
parent f3ab76cfd2
commit 0e0bf16957
7 changed files with 363 additions and 0 deletions
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9
pom.xml
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@@ -61,6 +61,8 @@
<jackson1.version>1.9.10</jackson1.version>
<jackson2.version>2.1.1</jackson2.version>
<jaxrs.version>1.0</jaxrs.version>
<jsonpath.version>0.8.1</jsonpath.version>
<minidevjson.version>1.1.1</minidevjson.version>
<bundlor.failOnWarnings>true</bundlor.failOnWarnings>
</properties>
@@ -132,6 +134,13 @@
<version>${jaxrs.version}</version>
<optional>true</optional>
</dependency>
<dependency>
<groupId>com.jayway.jsonpath</groupId>
<artifactId>json-path</artifactId>
<version>${jsonpath.version}</version>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.hamcrest</groupId>

63
src/main/java/org/springframework/hateoas/LinkDiscoverer.java Normal file
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@@ -0,0 +1,63 @@
/*
* Copyright 2012 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.io.InputStream;
import java.util.List;
/**
* Interface to allow discovering links by relation type from some source.
*
* @author Oliver Gierke
*/
public interface LinkDiscoverer {
/**
* Finds a single link with the given relation type in the given {@link String} representation.
*
* @param rel must not be {@literal null} or empty.
* @param representation must not be {@literal null} or empty.
* @return the first link with the given relation type found, or {@literal null} if none was found.
*/
Link findLinkWithRel(String rel, String representation);
/**
* Finds a single link with the given relation type in the given {@link InputStream} representation.
*
* @param rel must not be {@literal null} or empty.
* @param representation must not be {@literal null} or empty.
* @return the first link with the given relation type found, or {@literal null} if none was found.
*/
Link findLinkWithRel(String rel, InputStream representation);
/**
* Returns all links with the given relation type found in the given {@link String} representation.
*
* @param rel must not be {@literal null} or empty.
* @param representation must not be {@literal null} or empty.
* @return
*/
List<Link> findLinksWithRel(String rel, String representation);
/**
* Returns all links with the given relation type found in the given {@link InputStream} representation.
*
* @param rel must not be {@literal null} or empty.
* @param representation must not be {@literal null} or empty.
* @return
*/
List<Link> findLinksWithRel(String rel, InputStream representation);
}

31
src/main/java/org/springframework/hateoas/core/DefaultLinkDiscoverer.java Normal file
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@@ -0,0 +1,31 @@
/*
* Copyright 2012 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.core;
/**
* {@link JsonPathLinkDiscoverer} based on the default link representation we expose.
*
* @author Oliver Gierke
*/
public class DefaultLinkDiscoverer extends JsonPathLinkDiscoverer {
/**
* Creates a new {@link DefaultLinkDiscoverer}.
*/
public DefaultLinkDiscoverer() {
super("$links[?(@.rel == '%s')].href");
}
}

139
src/main/java/org/springframework/hateoas/core/JsonPathLinkDiscoverer.java Normal file
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@@ -0,0 +1,139 @@
/*
* Copyright 2012 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.core;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import net.minidev.json.JSONArray;
import org.springframework.hateoas.Link;
import org.springframework.hateoas.LinkDiscoverer;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;
import com.jayway.jsonpath.JsonPath;
/**
* {@link LinkDiscoverer} that uses {@link JsonPath} to find links inside a representation.
*
* @author Oliver Gierke
*/
public class JsonPathLinkDiscoverer implements LinkDiscoverer {
private final String pathTemplate;
/**
* Creates a new {@link JsonPathLinkDiscoverer} using the given path template. The template has to contain a single
* {@code %s} placeholder which will be replaced by the relation type.
*
* @param pathTemplate must not be {@literal null} or empty and contain a single placeholder.
*/
public JsonPathLinkDiscoverer(String pathTemplate) {
Assert.hasText(pathTemplate, "Path template must not be null!");
Assert.isTrue(StringUtils.countOccurrencesOf(pathTemplate, "%s") == 1,
"Path template must contain a single placeholder!");
this.pathTemplate = pathTemplate;
}
/*
* (non-Javadoc)
* @see org.springframework.hateoas.LinkDiscoverer#findLinkWithRel(java.lang.String, java.lang.String)
*/
@Override
public Link findLinkWithRel(String rel, String representation) {
List<Link> links = findLinksWithRel(rel, representation);
return links.isEmpty() ? null : links.get(0);
}
/*
* (non-Javadoc)
* @see org.springframework.hateoas.LinkDiscoverer#findLinkWithRel(java.lang.String, java.io.InputStream)
*/
@Override
public Link findLinkWithRel(String rel, InputStream representation) {
List<Link> links = findLinksWithRel(rel, representation);
return links.isEmpty() ? null : links.get(0);
}
/*
* (non-Javadoc)
* @see org.springframework.hateoas.LinkDiscoverer#findLinksWithRel(java.lang.String, java.lang.String)
*/
@Override
public List<Link> findLinksWithRel(String rel, String representation) {
Object parseResult = getExpression(rel).read(representation);
return createLinksFrom(parseResult, rel);
}
/*
* (non-Javadoc)
* @see org.springframework.hateoas.LinkDiscoverer#findLinksWithRel(java.lang.String, java.io.InputStream)
*/
@Override
public List<Link> findLinksWithRel(String rel, InputStream representation) {
try {
Object parseResult = getExpression(rel).read(representation);
return createLinksFrom(parseResult, rel);
} catch (IOException e) {
throw new RuntimeException(e);
}
}
/**
* Returns the {@link JsonPath} to find links with the given relation type.
*
* @param rel
* @return
*/
private JsonPath getExpression(String rel) {
return JsonPath.compile(String.format(pathTemplate, rel));
}
/**
* Creates {@link Link} instances from the given parse result.
*
* @param parseResult the result originating from parsing the source content using the JSON path expression.
* @param rel the relation type that was parsed for.
* @return
*/
private List<Link> createLinksFrom(Object parseResult, String rel) {
if (parseResult instanceof JSONArray) {
List<Link> links = new ArrayList<Link>();
JSONArray array = (JSONArray) parseResult;
for (Object element : array) {
links.add(new Link(element.toString(), rel));
}
return Collections.unmodifiableList(links);
}
Link link = new Link(parseResult.toString(), rel);
return Collections.unmodifiableList(Arrays.asList(link));
}
}

78
src/test/java/org/springframework/hateoas/core/DefaultLinkDiscovererUnitTest.java Normal file
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@@ -0,0 +1,78 @@
/*
* Copyright 2012 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.core;
import static org.hamcrest.Matchers.*;
import static org.junit.Assert.*;
import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.util.List;
import org.junit.Test;
import org.springframework.hateoas.Link;
import org.springframework.hateoas.LinkDiscoverer;
/**
* Unit tests for {@link DefaultLinkDiscoverer}.
*
* @author Oliver Gierke
*/
public class DefaultLinkDiscovererUnitTest {
static final String SAMPLE = "{ links : [ " + //
"{ rel : 'self', href : 'selfHref' }, " + //
"{ rel : 'relation', href : 'firstHref' }, " + //
"{ rel : 'relation', href : 'secondHref' }]}";
static final LinkDiscoverer discoverer = new DefaultLinkDiscoverer();
@Test
public void findsSingleLink() {
assertThat(discoverer.findLinkWithRel("self", SAMPLE), is(new Link("selfHref")));
List<Link> links = discoverer.findLinksWithRel("self", SAMPLE);
assertThat(links, hasSize(1));
assertThat(links, hasItem(new Link("selfHref")));
}
@Test
public void findsFirstLink() {
assertThat(discoverer.findLinkWithRel("relation", SAMPLE), is(new Link("firstHref", "relation")));
}
@Test
public void findsAllLinks() {
List<Link> links = discoverer.findLinksWithRel("relation", SAMPLE);
assertThat(links, hasSize(2));
assertThat(links, hasItems(new Link("firstHref", "relation"), new Link("secondHref", "relation")));
}
@Test
public void returnsForInexistingLink() {
assertThat(discoverer.findLinkWithRel("something", SAMPLE), is(nullValue()));
}
@Test
public void returnsForInxistingLinkFromInputStream() throws Exception {
InputStream inputStream = new ByteArrayInputStream(SAMPLE.getBytes("UTF-8"));
assertThat(discoverer.findLinkWithRel("something", inputStream), is(nullValue()));
}
}

41
src/test/java/org/springframework/hateoas/core/JsonPathLinkDiscovererUnitTests.java Normal file
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@@ -0,0 +1,41 @@
/*
* Copyright 2012 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.core;
import org.junit.Test;
/**
* Unit tests for {@link JsonPathLinkDiscoverer}.
*
* @author Oliver Gierke
*/
public class JsonPathLinkDiscovererUnitTests {
@Test(expected = IllegalArgumentException.class)
public void rejectsNullPattern() {
new JsonPathLinkDiscoverer(null);
}
@Test(expected = IllegalArgumentException.class)
public void rejectsPatternWithWithoutPlaceholder() {
new JsonPathLinkDiscoverer("$links");
}
@Test(expected = IllegalArgumentException.class)
public void rejectsPatternWithMultiplePlaceholders() {
new JsonPathLinkDiscoverer("$links%s%s");
}
}

2
template.mf
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@@ -4,7 +4,9 @@ Bundle-Vendor: SpringSource
Bundle-ManifestVersion: 2
Import-Template:
com.fasterxml.jackson.*;version="${jackson2.version:[=.=.=,+1.0.0)}";resolution:=optional,
com.jayway.jsonpath.*;version="${jsonpath.version:[=.=.=,+1.0.0)}";resolution:=optional,
javax.ws.rs.*;version="${jaxrs.version:[=.=.=,+1.0.0)}";resolution:=optional,
javax.xml.bind.*;version="0",
net.minidev.json.*;version="${minidevjson.version:[=.=.=,+1.0.0)}";resolution:=optional,
org.springframework.*;version="${spring.version:[=.=.=,+1.0.0)}";resolution:=optional,
org.codehaus.jackson.*;version="${jackson1.version:[=.=.=,+1.0.0)}";resolution:=optional