From 212daa19954ec639e493554ade50149995f4e802 Mon Sep 17 00:00:00 2001
From: Arjen Poutsma <apoutsma@vmware.com>
Date: Tue, 23 Mar 2010 11:15:13 +0000
Subject: [PATCH] SPR-7002 - RestTemplate fails to convert properly for Generic
 Type Container with MappingJacksonHttpMessageConverter

---
 .../MappingJacksonHttpMessageConverter.java   | 29 +++++++++++++---
 ...ppingJacksonHttpMessageConverterTests.java | 33 ++++++++++++++++++-
 2 files changed, 57 insertions(+), 5 deletions(-)

diff --git a/org.springframework.web/src/main/java/org/springframework/http/converter/json/MappingJacksonHttpMessageConverter.java b/org.springframework.web/src/main/java/org/springframework/http/converter/json/MappingJacksonHttpMessageConverter.java
index 00635716e07..deafebd8e53 100644
--- a/org.springframework.web/src/main/java/org/springframework/http/converter/json/MappingJacksonHttpMessageConverter.java
+++ b/org.springframework.web/src/main/java/org/springframework/http/converter/json/MappingJacksonHttpMessageConverter.java
@@ -86,13 +86,34 @@ public class MappingJacksonHttpMessageConverter extends AbstractHttpMessageConve
 		this.prefixJson = prefixJson;
 	}
 
-
 	@Override
 	public boolean canRead(Class<?> clazz, MediaType mediaType) {
-		JavaType javaType = TypeFactory.fromClass(clazz);
+		JavaType javaType = getJavaType(clazz);
 		return this.objectMapper.canDeserialize(javaType) && canRead(mediaType);
 	}
 
+	/**
+	 * Returns the Jackson {@link JavaType} for the specific class.
+	 *
+	 * <p>Default implementation returns {@link TypeFactory#type(java.lang.reflect.Type)}, but this can be overridden
+	 * in subclasses, to allow for custom generic collection handling. For instance:
+	 * <pre class="code">
+	 * protected JavaType getJavaType(Class&lt;?&gt; clazz) {
+	 *   if (List.class.isAssignableFrom(clazz)) {
+	 *     return TypeFactory.collectionType(ArrayList.class, MyBean.class);
+	 *   } else {
+	 *     return super.getJavaType(clazz);
+	 *   }
+	 * }
+	 * </pre>
+	 *
+	 * @param clazz the class to return the java type for
+	 * @return the java type
+	 */
+	protected JavaType getJavaType(Class<?> clazz) {
+		return TypeFactory.type(clazz);
+	}
+
 	@Override
 	public boolean canWrite(Class<?> clazz, MediaType mediaType) {
 		return this.objectMapper.canSerialize(clazz) && canWrite(mediaType);
@@ -107,8 +128,8 @@ public class MappingJacksonHttpMessageConverter extends AbstractHttpMessageConve
 	@Override
 	protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage)
 			throws IOException, HttpMessageNotReadableException {
-
-		return this.objectMapper.readValue(inputMessage.getBody(), clazz);
+		JavaType javaType = getJavaType(clazz);
+		return this.objectMapper.readValue(inputMessage.getBody(), javaType);
 	}
 
 	@Override
diff --git a/org.springframework.web/src/test/java/org/springframework/http/converter/json/MappingJacksonHttpMessageConverterTests.java b/org.springframework.web/src/test/java/org/springframework/http/converter/json/MappingJacksonHttpMessageConverterTests.java
index 32fb7fd3b16..a79ec58b66f 100644
--- a/org.springframework.web/src/test/java/org/springframework/http/converter/json/MappingJacksonHttpMessageConverterTests.java
+++ b/org.springframework.web/src/test/java/org/springframework/http/converter/json/MappingJacksonHttpMessageConverterTests.java
@@ -23,6 +23,8 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+import org.codehaus.jackson.map.type.TypeFactory;
+import org.codehaus.jackson.type.JavaType;
 import static org.junit.Assert.*;
 import org.junit.Before;
 import org.junit.Test;
@@ -56,7 +58,6 @@ public class MappingJacksonHttpMessageConverterTests {
 	}
 
 	@Test
-	@SuppressWarnings("unchecked")
 	public void readTyped() throws IOException {
 		String body =
 				"{\"bytes\":\"AQI=\",\"array\":[\"Foo\",\"Bar\"],\"number\":42,\"string\":\"Foo\",\"bool\":true,\"fraction\":42.0}";
@@ -71,6 +72,36 @@ public class MappingJacksonHttpMessageConverterTests {
 		assertArrayEquals(new byte[]{0x1, 0x2}, result.getBytes());
 	}
 
+	@Test
+	@SuppressWarnings("unchecked")
+	public void readGenerics() throws IOException {
+		converter = new MappingJacksonHttpMessageConverter() {
+			@Override
+			protected JavaType getJavaType(Class<?> clazz) {
+				if (List.class.isAssignableFrom(clazz)) {
+					return TypeFactory.collectionType(ArrayList.class, MyBean.class);
+				}
+				else {
+					return super.getJavaType(clazz);
+				}
+			}
+		};
+		String body =
+				"[{\"bytes\":\"AQI=\",\"array\":[\"Foo\",\"Bar\"],\"number\":42,\"string\":\"Foo\",\"bool\":true,\"fraction\":42.0}]";
+		MockHttpInputMessage inputMessage = new MockHttpInputMessage(body.getBytes("UTF-8"));
+		inputMessage.getHeaders().setContentType(new MediaType("application", "json"));
+
+		List<MyBean> results = (List<MyBean>) converter.read(List.class, inputMessage);
+		assertEquals(1, results.size());
+		MyBean result = results.get(0);
+		assertEquals("Foo", result.getString());
+		assertEquals(42, result.getNumber());
+		assertEquals(42F, result.getFraction(), 0F);
+		assertArrayEquals(new String[]{"Foo", "Bar"}, result.getArray());
+		assertTrue(result.isBool());
+		assertArrayEquals(new byte[]{0x1, 0x2}, result.getBytes());
+	}
+
 	@Test
 	@SuppressWarnings("unchecked")
 	public void readUntyped() throws IOException {