Introduced "jsonPrefix" bean property

This change involves a modification of the "writeContent" template method to include the "jsonPrefix" String instead of the "prefixJson" boolean flag. Since said template method has only been introduced in 3.2.2, this change should hopefully not be a problem.

Issue: SPR-10567
(cherry picked from commit 28164b4)

Author: jhoeller

spring-webmvc/src/main/java/org/springframework/web/servlet/view/json/MappingJackson2JsonView.java

@@ -65,7 +65,7 @@ public class MappingJackson2JsonView extends AbstractView {
 
 	private JsonEncoding encoding = JsonEncoding.UTF8;
 
-	private boolean prefixJson = false;
+	private String jsonPrefix;
 
 	private Boolean prettyPrint;
 
@@ -123,22 +123,32 @@ public final JsonEncoding getEncoding() {
 		return this.encoding;
 	}
 
+	/**
+	 * Specify a custom prefix to use for this view's JSON output.
+	 * Default is none.
+	 * @see #setPrefixJson
+	 */
+	public void setJsonPrefix(String jsonPrefix) {
+		this.jsonPrefix = jsonPrefix;
+	}
+
 	/**
 	 * Indicates whether the JSON output by this view should be prefixed with <tt>"{} && "</tt>.
 	 * Default is {@code false}.
 	 * <p>Prefixing the JSON string in this manner is used to help prevent JSON Hijacking.
 	 * The prefix renders the string syntactically invalid as a script so that it cannot be hijacked.
 	 * This prefix does not affect the evaluation of JSON, but if JSON validation is performed
 	 * on the string, the prefix would need to be ignored.
+	 * @see #setJsonPrefix
 	 */
 	public void setPrefixJson(boolean prefixJson) {
-		this.prefixJson = prefixJson;
+		this.jsonPrefix = "{} && ";
 	}
 
 	/**
 	 * Whether to use the default pretty printer when writing JSON.
 	 * This is a shortcut for setting up an {@code ObjectMapper} as follows:
-	 * <pre>
+	 * <pre class="code">
 	 * ObjectMapper mapper = new ObjectMapper();
 	 * mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
 	 * </pre>
@@ -244,7 +254,7 @@ protected void renderMergedOutputModel(Map<String, Object> model, HttpServletReq
 
 		OutputStream stream = (this.updateContentLength ? createTemporaryOutputStream() : response.getOutputStream());
 		Object value = filterModel(model);
-		writeContent(stream, value, this.prefixJson);
+		writeContent(stream, value, this.jsonPrefix);
 		if (this.updateContentLength) {
 			writeToResponse(response, (ByteArrayOutputStream) stream);
 		}
@@ -273,11 +283,11 @@ protected Object filterModel(Map<String, Object> model) {
 	 * Write the actual JSON content to the stream.
 	 * @param stream the output stream to use
 	 * @param value the value to be rendered, as returned from {@link #filterModel}
-	 * @param prefixJson whether the JSON output by this view should be prefixed
-	 * with <tt>"{} && "</tt> (as indicated through {@link #setPrefixJson})
+	 * @param jsonPrefix the prefix for this view's JSON output
+	 * (as indicated through {@link #setJsonPrefix}/{@link #setPrefixJson})
 	 * @throws IOException if writing failed
 	 */
-	protected void writeContent(OutputStream stream, Object value, boolean prefixJson) throws IOException {
+	protected void writeContent(OutputStream stream, Object value, String jsonPrefix) throws IOException {
 		JsonGenerator generator = this.objectMapper.getJsonFactory().createJsonGenerator(stream, this.encoding);
 
 		// A workaround for JsonGenerators not applying serialization features
@@ -286,8 +296,8 @@ protected void writeContent(OutputStream stream, Object value, boolean prefixJso
 			generator.useDefaultPrettyPrinter();
 		}
 
-		if (prefixJson) {
-			generator.writeRaw("{} && ");
+		if (jsonPrefix != null) {
+			generator.writeRaw(jsonPrefix);
 		}
 		this.objectMapper.writeValue(generator, value);
 	}

spring-webmvc/src/main/java/org/springframework/web/servlet/view/json/MappingJacksonJsonView.java

@@ -65,7 +65,7 @@ public class MappingJacksonJsonView extends AbstractView {
 
 	private JsonEncoding encoding = JsonEncoding.UTF8;
 
-	private boolean prefixJson = false;
+	private String jsonPrefix;
 
 	private Boolean prettyPrint;
 
@@ -123,16 +123,26 @@ public final JsonEncoding getEncoding() {
 		return this.encoding;
 	}
 
+	/**
+	 * Specify a custom prefix to use for this view's JSON output.
+	 * Default is none.
+	 * @see #setPrefixJson
+	 */
+	public void setJsonPrefix(String jsonPrefix) {
+		this.jsonPrefix = jsonPrefix;
+	}
+
 	/**
 	 * Indicates whether the JSON output by this view should be prefixed with <tt>"{} && "</tt>.
 	 * Default is {@code false}.
 	 * <p>Prefixing the JSON string in this manner is used to help prevent JSON Hijacking.
 	 * The prefix renders the string syntactically invalid as a script so that it cannot be hijacked.
 	 * This prefix does not affect the evaluation of JSON, but if JSON validation is performed
 	 * on the string, the prefix would need to be ignored.
+	 * @see #setJsonPrefix
 	 */
 	public void setPrefixJson(boolean prefixJson) {
-		this.prefixJson = prefixJson;
+		this.jsonPrefix = "{} && ";
 	}
 
 	/**
@@ -244,7 +254,7 @@ protected void renderMergedOutputModel(Map<String, Object> model, HttpServletReq
 
 		OutputStream stream = (this.updateContentLength ? createTemporaryOutputStream() : response.getOutputStream());
 		Object value = filterModel(model);
-		writeContent(stream, value, this.prefixJson);
+		writeContent(stream, value, this.jsonPrefix);
 		if (this.updateContentLength) {
 			writeToResponse(response, (ByteArrayOutputStream) stream);
 		}
@@ -273,11 +283,11 @@ protected Object filterModel(Map<String, Object> model) {
 	 * Write the actual JSON content to the stream.
 	 * @param stream the output stream to use
 	 * @param value the value to be rendered, as returned from {@link #filterModel}
-	 * @param prefixJson whether the JSON output by this view should be prefixed
-	 * with <tt>"{} && "</tt> (as indicated through {@link #setPrefixJson})
+	 * @param jsonPrefix the prefix for this view's JSON output
+	 * (as indicated through {@link #setJsonPrefix}/{@link #setPrefixJson})
 	 * @throws IOException if writing failed
 	 */
-	protected void writeContent(OutputStream stream, Object value, boolean prefixJson) throws IOException {
+	protected void writeContent(OutputStream stream, Object value, String jsonPrefix) throws IOException {
 		JsonGenerator generator = this.objectMapper.getJsonFactory().createJsonGenerator(stream, this.encoding);
 
 		// A workaround for JsonGenerators not applying serialization features
@@ -286,8 +296,8 @@ protected void writeContent(OutputStream stream, Object value, boolean prefixJso
 			generator.useDefaultPrettyPrinter();
 		}
 
-		if (prefixJson) {
-			generator.writeRaw("{} && ");
+		if (jsonPrefix != null) {
+			generator.writeRaw(jsonPrefix);
 		}
 		this.objectMapper.writeValue(generator, value);
 	}