使用 RestTemplate 与对象作为数据和 application/x-www-form-urlencoded 内容类型? [英] Use RestTemplate with object as data and application/x-www-form-urlencoded content type?

问题描述

我需要通过内容类型为 application/x-www-form-urlencodedRestTemplate 发布一个对象(例如不是 MultiValueMap)代码>.当我尝试这样做时......

I need to post an object (e.g. not a MultiValueMap) via a RestTemplate with the content type application/x-www-form-urlencoded. When I try to do so ...

HttpHeaders headers = new HttpHeaders();
HttpEntity request;

headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED)

// data is some generic type
request = new HttpEntity<>(data, headers);

// clazz is the Class<T> being returned
restTemplate.exchange(url, method, request, clazz)

...我收到以下错误:

... I get the following error:

org.springframework.web.client.RestClientException:无法写入请求:没有找到适合请求类型 [com.whatever.MyRequestPayload] 和内容类型 [application/x-www-form-urlencoded] 的 HttpMessageConverter

org.springframework.web.client.RestClientException: Could not write request: no suitable HttpMessageConverter found for request type [com.whatever.MyRequestPayload] and content type [application/x-www-form-urlencoded]

这是我在 restTemplate.getMessageConverters() 中看到的:

Here is what I see within restTemplate.getMessageConverters():

为什么我不想提供 MultiValueMap? 两个原因:

Why don't I want to provide a MultiValueMap? Two reasons:

1. 这是用于向多个端点发送请求的通用代码，因此专门为 x-www-form-urlencoded 添加重载只会使事情复杂化
2. 似乎我不应该 - 我只是不知道需要使用哪个 HttpMessageConverter 来支持将对象转换为 x-www-form-urlencoded 字符串

1. this is general purpose code which is used to send requests to multiple endpoints, so adding an overload specifically for x-www-form-urlencoded will only complicate things
2. it doesn't seem like I should have to -- I just don't know which HttpMessageConverter needs to be used to support converting objects to a x-www-form-urlencoded string

推荐答案

我最终不得不编写一个自定义 HTTP 消息转换器，它接受任何对象并将其作为 www-form-urlencoded 内容写出到请求正文:

用法

I ended up having to write a custom HTTP message converter which takes any object and writes it out as www-form-urlencoded content to the request body:

RestTemplate template = new RestTemplate(...);

template.getMessageConverters().add(new ObjectToUrlEncodedConverter(mapper));

ObjectToUrlEncodedConverter

import com.fasterxml.jackson.annotation.JsonAnySetter;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;
import sun.reflect.generics.reflectiveObjects.NotImplementedException;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.util.Collections;
import java.util.List;

public class ObjectToUrlEncodedConverter implements HttpMessageConverter
{
    private static final String Encoding = "UTF-8";

    private final ObjectMapper mapper;

    public ObjectToUrlEncodedConverter(ObjectMapper mapper)
    {
        this.mapper = mapper;
    }

    @Override
    public boolean canRead(Class clazz, MediaType mediaType)
    {
        return false;
    }

    @Override
    public boolean canWrite(Class clazz, MediaType mediaType)
    {
        return getSupportedMediaTypes().contains(mediaType);
    }

    @Override
    public List<MediaType> getSupportedMediaTypes()
    {
        return Collections.singletonList(MediaType.APPLICATION_FORM_URLENCODED);
    }

    @Override
    public Object read(Class clazz, HttpInputMessage inputMessage) throws HttpMessageNotReadableException
    {
        throw new NotImplementedException();
    }

    @Override
    public void write(Object o, MediaType contentType, HttpOutputMessage outputMessage) throws HttpMessageNotWritableException
    {
        if (o != null)
        {
            String body = mapper
                .convertValue(o, UrlEncodedWriter.class)
                .toString();

            try
            {
                outputMessage.getBody().write(body.getBytes(Encoding));
            }
            catch (IOException e)
            {
                // if UTF-8 is not supporter then I give up
            }
        }
    }

    private static class UrlEncodedWriter
    {
        private final StringBuilder out = new StringBuilder();

        @JsonAnySetter
        public void write(String name, Object property) throws UnsupportedEncodingException
        {
            if (out.length() > 0)
            {
                out.append("&");
            }

            out
                .append(URLEncoder.encode(name, Encoding))
                .append("=");

            if (property != null)
            {
                out.append(URLEncoder.encode(property.toString(), Encoding));
            }
        }

        @Override
        public String toString()
        {
            return out.toString();
        }
    }
}

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