Avoid String allocations with Assert.state()

spring-web/src/main/java/org/springframework/http/converter/json/AbstractJackson2HttpMessageConverter.java

@@ -356,7 +356,7 @@ public abstract class AbstractJackson2HttpMessageConverter extends AbstractGener
 		Charset charset = getCharset(contentType);
 
 		ObjectMapper objectMapper = selectObjectMapper(javaType.getRawClass(), contentType);
-		Assert.state(objectMapper != null, "No ObjectMapper for " + javaType);
+		Assert.state(objectMapper != null, () -> "No ObjectMapper for " + javaType);
 
 		boolean isUnicode = ENCODINGS.containsKey(charset.name()) ||
 				"UTF-16".equals(charset.name()) ||
@@ -419,7 +419,7 @@ public abstract class AbstractJackson2HttpMessageConverter extends AbstractGener
 		Class<?> clazz = (object instanceof MappingJacksonValue ?
 				((MappingJacksonValue) object).getValue().getClass() : object.getClass());
 		ObjectMapper objectMapper = selectObjectMapper(clazz, contentType);
-		Assert.state(objectMapper != null, "No ObjectMapper for " + clazz.getName());
+		Assert.state(objectMapper != null, () -> "No ObjectMapper for " + clazz.getName());
 
 		OutputStream outputStream = StreamUtils.nonClosing(outputMessage.getBody());
 		try (JsonGenerator generator = objectMapper.getFactory().createGenerator(outputStream, encoding)) {

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ResponseBodyEmitter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -193,8 +193,7 @@ public class ResponseBodyEmitter {
 	 * @throws java.lang.IllegalStateException wraps any other errors
 	 */
 	public synchronized void send(Object object, @Nullable MediaType mediaType) throws IOException {
-		Assert.state(!this.complete,
+		Assert.state(!this.complete, () -> "ResponseBodyEmitter has already completed" +
-				"ResponseBodyEmitter has already completed" +
 						(this.failure != null ? " with error: " + this.failure : ""));
 		sendInternal(object, mediaType);
 	}