Respect MimeType charset in Jackson codecs

Before this commit, Jackson2CodecSupport and subclasses
did not check media type encoding in the supportsMimeType
method (called from canEncode/canDecode).
As a result, the encoder reported that it can write
(for instance) "application/json;charset=ISO-8859-1", but in practice
wrote the default charset (UTF-8).

This commit fixes that bug.

Closes: gh-25076

spring-web/src/main/java/org/springframework/http/codec/json/Jackson2CodecSupport.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -19,12 +19,18 @@
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Type;
 import java.nio.charset.StandardCharsets;
+import java.nio.charset.Charset;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.EnumSet;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
 
 import com.fasterxml.jackson.annotation.JsonView;
+import com.fasterxml.jackson.core.JsonEncoding;
 import com.fasterxml.jackson.databind.JavaType;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.type.TypeFactory;
@@ -64,6 +70,9 @@ public abstract class Jackson2CodecSupport {
 					new MimeType("application", "json", StandardCharsets.UTF_8),
 					new MimeType("application", "*+json", StandardCharsets.UTF_8)));
 
+	private static final Map<String, JsonEncoding> ENCODINGS = jsonEncodings();
+
+
 
 	protected final Log logger = HttpLogging.forLogName(getClass());
 
@@ -96,7 +105,17 @@ protected List<MimeType> getMimeTypes() {
 
 
 	protected boolean supportsMimeType(@Nullable MimeType mimeType) {
-		return (mimeType == null || this.mimeTypes.stream().anyMatch(m -> m.isCompatibleWith(mimeType)));
+		if (mimeType == null) {
+			return true;
+		}
+		else if (this.mimeTypes.stream().noneMatch(m -> m.isCompatibleWith(mimeType))) {
+			return false;
+		}
+		else if (mimeType.getCharset() != null) {
+			Charset charset = mimeType.getCharset();
+			return ENCODINGS.containsKey(charset.name());
+		}
+		return true;
 	}
 
 	protected JavaType getJavaType(Type type, @Nullable Class<?> contextClass) {
@@ -125,4 +144,10 @@ protected MethodParameter getParameter(ResolvableType type) {
 	@Nullable
 	protected abstract <A extends Annotation> A getAnnotation(MethodParameter parameter, Class<A> annotType);
 
+	private static Map<String, JsonEncoding> jsonEncodings() {
+		return EnumSet.allOf(JsonEncoding.class).stream()
+				.collect(Collectors.toMap(JsonEncoding::getJavaName, Function.identity()));
+	}
+
+
 }

spring-web/src/test/java/org/springframework/http/codec/json/Jackson2JsonDecoderTests.java

@@ -89,6 +89,11 @@ public void canDecode() {
 
 		assertFalse(decoder.canDecode(forClass(String.class), null));
 		assertFalse(decoder.canDecode(forClass(Pojo.class), APPLICATION_XML));
+		assertTrue(this.decoder.canDecode(forClass(Pojo.class),
+				new MediaType("application", "json", StandardCharsets.UTF_8)));
+		assertFalse(this.decoder.canDecode(forClass(Pojo.class),
+				new MediaType("application", "json", StandardCharsets.ISO_8859_1)));
+
 	}
 
 	@Test  // SPR-15866

spring-web/src/test/java/org/springframework/http/codec/json/Jackson2JsonEncoderTests.java

@@ -71,6 +71,11 @@ public void canEncode() {
 		assertTrue(this.encoder.canEncode(pojoType, APPLICATION_STREAM_JSON));
 		assertTrue(this.encoder.canEncode(pojoType, null));
 
+		assertTrue(this.encoder.canEncode(ResolvableType.forClass(Pojo.class),
+				new MediaType("application", "json", StandardCharsets.UTF_8)));
+		assertFalse(this.encoder.canEncode(ResolvableType.forClass(Pojo.class),
+				new MediaType("application", "json", StandardCharsets.ISO_8859_1)));
+
 		// SPR-15464
 		assertTrue(this.encoder.canEncode(ResolvableType.NONE, null));
 

spring-web/src/test/java/org/springframework/http/codec/json/Jackson2SmileDecoderTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.http.codec.json;
 
+import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.List;
 
@@ -64,8 +65,14 @@ public void canDecode() {
 
 		assertFalse(decoder.canDecode(forClass(String.class), null));
 		assertFalse(decoder.canDecode(forClass(Pojo.class), APPLICATION_JSON));
+
+		assertTrue(this.decoder.canDecode(ResolvableType.forClass(Pojo.class),
+				new MimeType("application", "x-jackson-smile", StandardCharsets.UTF_8)));
+		assertFalse(this.decoder.canDecode(ResolvableType.forClass(Pojo.class),
+				new MimeType("application", "x-jackson-smile", StandardCharsets.ISO_8859_1)));
 	}
 
+
 	@Override
 	public void decode() {
 		Flux<DataBuffer> input = Flux.just(this.pojo1, this.pojo2)

spring-web/src/test/java/org/springframework/http/codec/json/Jackson2SmileEncoderTests.java

@@ -18,6 +18,7 @@
 
 import java.io.IOException;
 import java.io.UncheckedIOException;
+import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.List;
 
@@ -70,6 +71,11 @@ public void canEncode() {
 		assertTrue(this.encoder.canEncode(pojoType, STREAM_SMILE_MIME_TYPE));
 		assertTrue(this.encoder.canEncode(pojoType, null));
 
+		assertTrue(this.encoder.canEncode(ResolvableType.forClass(Pojo.class),
+				new MimeType("application", "x-jackson-smile", StandardCharsets.UTF_8)));
+		assertFalse(this.encoder.canEncode(ResolvableType.forClass(Pojo.class),
+				new MimeType("application", "x-jackson-smile", StandardCharsets.ISO_8859_1)));
+
 		// SPR-15464
 		assertTrue(this.encoder.canEncode(ResolvableType.NONE, null));
 	}