RestTemplate响应中如何获取输入流InputStream

RestTemplate rest = new RestTemplate();

String message = rest.getForObject(url, String.class);
// or
String message = rest.postForObject(url, paramObject, String.class);

ResponseEntity<Resource> entity = rest.postForEntity(url, paramObject, Resource.class);
InputStream in = entity.getBody().getInputStream();

if (entity.getStatusCode().equals(HttpStatus.OK)) {
    // ...
}

// 这里查询用的是Http语义GET，对应的新增为POST，删除为DELETE，修改为PUT
GET
/order/123

/order/queryOrder/123

public interface HttpMessageConverter<T> {
	boolean canRead(Class<?> clazz, @Nullable MediaType mediaType);
	boolean canWrite(Class<?> clazz, @Nullable MediaType mediaType);
	List<MediaType> getSupportedMediaTypes();
	T read(Class<? extends T> clazz, HttpInputMessage inputMessage)
			throws IOException, HttpMessageNotReadableException;
	void write(T t, @Nullable MediaType contentType, HttpOutputMessage outputMessage)
			throws IOException, HttpMessageNotWritableException;
}

// 判断当前Converter是否支持此类型的转换，只有是String时才会支持
@Override
public boolean supports(Class<?> clazz) {
	return String.class == clazz;
}

// 从HttpInputMessage读取输入流，并转化为String对象
@Override
protected String readInternal(Class<? extends String> clazz, HttpInputMessage inputMessage) throws IOException {
	Charset charset = getContentTypeCharset(inputMessage.getHeaders().getContentType());
	return StreamUtils.copyToString(inputMessage.getBody(), charset);
}

// 从InputStream中读取原始的报文数据
public static String copyToString(@Nullable InputStream in, Charset charset) throws IOException {
    if (in == null) {
        return "";
    } else {
        StringBuilder out = new StringBuilder();
        InputStreamReader reader = new InputStreamReader(in, charset);
        char[] buffer = new char[4096];

        int charsRead;
        while((charsRead = reader.read(buffer)) != -1) {
            out.append(buffer, 0, charsRead);
        }

        return out.toString();
    }
}