#133 - Made JsonPathLinkDiscoverer more robust.

JsonPathLinkDiscoverer now handles InvalidPathExceptions that might occur if the representation doesn't contain the link container element.

src/main/java/org/springframework/hateoas/core/JsonPathLinkDiscoverer.java

@@ -30,6 +30,7 @@ import org.springframework.http.MediaType;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
+import com.jayway.jsonpath.InvalidPathException;
 import com.jayway.jsonpath.JsonPath;
 
 /**
@@ -88,8 +89,12 @@ public class JsonPathLinkDiscoverer implements LinkDiscoverer {
 	@Override
 	public List<Link> findLinksWithRel(String rel, String representation) {
 
-		Object parseResult = getExpression(rel).read(representation);
-		return createLinksFrom(parseResult, rel);
+		try {
+			Object parseResult = getExpression(rel).read(representation);
+			return createLinksFrom(parseResult, rel);
+		} catch (InvalidPathException e) {
+			return Collections.emptyList();
+		}
 	}
 
 	/* 

src/test/java/org/springframework/hateoas/core/AbstractLinkDiscovererUnitTest.java

@@ -22,6 +22,7 @@ import java.io.ByteArrayInputStream;
 import java.io.InputStream;
 import java.util.List;
 
+import org.hamcrest.Matchers;
 import org.junit.Test;
 import org.springframework.hateoas.Link;
 import org.springframework.hateoas.LinkDiscoverer;
@@ -63,12 +64,20 @@ public abstract class AbstractLinkDiscovererUnitTest {
 	}
 
 	@Test
-	public void returnsForInxistingLinkFromInputStream() throws Exception {
+	public void returnsForInexistingLinkFromInputStream() throws Exception {
 
 		InputStream inputStream = new ByteArrayInputStream(getInputString().getBytes("UTF-8"));
 		assertThat(getDiscoverer().findLinkWithRel("something", inputStream), is(nullValue()));
 	}
 
+	@Test
+	public void returnsNullForNonExistingLinkContainer() {
+
+		assertThat(getDiscoverer().findLinksWithRel("something", getInputStringWithoutLinkContainer()),
+				is(Matchers.<Link> empty()));
+		assertThat(getDiscoverer().findLinkWithRel("something", getInputStringWithoutLinkContainer()), is(nullValue()));
+	}
+
 	/**
 	 * Return the {@link LinkDiscoverer} to be tested.
 	 * 
@@ -82,4 +91,6 @@ public abstract class AbstractLinkDiscovererUnitTest {
 	 * @return
 	 */
 	protected abstract String getInputString();
+
+	protected abstract String getInputStringWithoutLinkContainer();
 }

src/test/java/org/springframework/hateoas/hal/HalLinkDiscovererUnitTest.java

@@ -40,4 +40,9 @@ public class HalLinkDiscovererUnitTest extends AbstractLinkDiscovererUnitTest {
 	protected String getInputString() {
 		return SAMPLE;
 	}
+
+	@Override
+	protected String getInputStringWithoutLinkContainer() {
+		return "{}";
+	}
 }