org.springframework.http.converter.StringHttpMessageConverter Maven / Gradle / Ivy
/*
* Copyright 2002-2024 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.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.http.converter;
import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.StreamUtils;
/**
* Implementation of {@link HttpMessageConverter} that can read and write strings.
*
* By default, this converter supports all media types (*/*),
* and writes with a {@code Content-Type} of {@code text/plain}. This can be overridden
* by setting the {@link #setSupportedMediaTypes supportedMediaTypes} property.
*
* @author Arjen Poutsma
* @author Juergen Hoeller
* @since 3.0
*/
public class StringHttpMessageConverter extends AbstractHttpMessageConverter {
private static final MediaType APPLICATION_PLUS_JSON = new MediaType("application", "*+json");
/**
* The default charset used by the converter.
*/
public static final Charset DEFAULT_CHARSET = StandardCharsets.ISO_8859_1;
@Nullable
private volatile List availableCharsets;
private boolean writeAcceptCharset = false;
/**
* A default constructor that uses {@code "ISO-8859-1"} as the default charset.
* @see #StringHttpMessageConverter(Charset)
*/
public StringHttpMessageConverter() {
this(DEFAULT_CHARSET);
}
/**
* A constructor accepting a default charset to use if the requested content
* type does not specify one.
*/
public StringHttpMessageConverter(Charset defaultCharset) {
super(defaultCharset, MediaType.TEXT_PLAIN, MediaType.ALL);
}
/**
* Whether the {@code Accept-Charset} header should be written to any outgoing
* request sourced from the value of {@link Charset#availableCharsets()}.
* The behavior is suppressed if the header has already been set.
* As of 5.2, by default is set to {@code false}.
*/
public void setWriteAcceptCharset(boolean writeAcceptCharset) {
this.writeAcceptCharset = writeAcceptCharset;
}
@Override
public boolean supports(Class clazz) {
return String.class == clazz;
}
@Override
protected String readInternal(Class clazz, HttpInputMessage inputMessage) throws IOException {
Charset charset = getContentTypeCharset(inputMessage.getHeaders().getContentType());
return StreamUtils.copyToString(inputMessage.getBody(), charset);
}
@Override
protected Long getContentLength(String str, @Nullable MediaType contentType) {
Charset charset = getContentTypeCharset(contentType);
return (long) str.getBytes(charset).length;
}
@Override
protected void addDefaultHeaders(HttpHeaders headers, String s, @Nullable MediaType type) throws IOException {
if (headers.getContentType() == null ) {
if (type != null && type.isConcrete() && (type.isCompatibleWith(MediaType.APPLICATION_JSON) ||
type.isCompatibleWith(APPLICATION_PLUS_JSON))) {
// Prevent charset parameter for JSON.
headers.setContentType(type);
}
}
super.addDefaultHeaders(headers, s, type);
}
@Override
protected void writeInternal(String str, HttpOutputMessage outputMessage) throws IOException {
HttpHeaders headers = outputMessage.getHeaders();
if (this.writeAcceptCharset && headers.get(HttpHeaders.ACCEPT_CHARSET) == null) {
headers.setAcceptCharset(getAcceptedCharsets());
}
Charset charset = getContentTypeCharset(headers.getContentType());
StreamUtils.copy(str, charset, outputMessage.getBody());
}
/**
* Return the list of supported {@link Charset Charsets}.
*
By default, returns {@link Charset#availableCharsets()}.
* Can be overridden in subclasses.
* @return the list of accepted charsets
*/
protected List getAcceptedCharsets() {
List charsets = this.availableCharsets;
if (charsets == null) {
charsets = new ArrayList<>(Charset.availableCharsets().values());
this.availableCharsets = charsets;
}
return charsets;
}
private Charset getContentTypeCharset(@Nullable MediaType contentType) {
if (contentType != null) {
Charset charset = contentType.getCharset();
if (charset != null) {
return charset;
}
else if (contentType.isCompatibleWith(MediaType.APPLICATION_JSON) ||
contentType.isCompatibleWith(APPLICATION_PLUS_JSON)) {
// Matching to AbstractJackson2HttpMessageConverter#DEFAULT_CHARSET
return StandardCharsets.UTF_8;
}
}
Charset charset = getDefaultCharset();
Assert.state(charset != null, "No default charset");
return charset;
}
}