为了统一接口请求格式，要将Spring Security获取token接口改成接收JSON格式，如下是我的几种尝试，最后一种为简单有效办法。

在Spring Cloud Gateway处理JSON转application/x-www-form-urlencoded(无效)

代码是这样的

@Component
@RequiredArgsConstructor(onConstructor_ = @Autowired)
public class PlatformRequestGlobalFilter implements GlobalFilter, Ordered {
    
    

    @Value("${project.gateway.filter.order: -10}")
    private int order;

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
    
    
        ServerHttpRequest request = exchange.getRequest();
        return DataBufferUtils.join(request.getBody())
                .flatMap(dataBuffer -> {
    
    
                    byte[] bytes = new byte[dataBuffer.readableByteCount()];
                    dataBuffer.read(bytes);
                    String json = new String(bytes, StandardCharsets.UTF_8);
                    DataBufferUtils.release(dataBuffer);
                    try {
    
    
                        //json参数转换
                        HashMap<String, String> result =  new ObjectMapper().readValue(json, HashMap.class);
                        ServerHttpRequest mutatedRequest = new ServerHttpRequestDecorator(exchange.getRequest()) {
    
    
                            @Override
                            public HttpHeaders getHeaders() {
    
    
                                HttpHeaders httpHeaders = new HttpHeaders();
                                httpHeaders.putAll(super.getHeaders());
                                httpHeaders.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
                                return httpHeaders;
                            }

                            @Override
                            public URI getURI() {
    
    
                                //json参数转换成key=value&key1=value1形式
                                String params = mapToString(result);
                                //只是测试，地址写死了，参数是拼接的
                                return URI.create("http://localhost:8010/oauth/token?" + params);
                            }
                        };
                        //替换request
                        return chain.filter(exchange.mutate().request(mutatedRequest).build());
                    } catch (JsonProcessingException e) {
    
    
                        e.printStackTrace();
                    }
                    
                    return chain.filter(exchange);

                });
    }

    private String mapToString(HashMap<String, String> map) {
    
    
        final StringBuilder strBuilder = StrUtil.builder();
        boolean isFirst = true;
        if (MapUtil.isNotEmpty(map)) {
    
    
            for (Entry<String, String> entry : map.entrySet()) {
    
    
                if (entry.getKey() != null && entry.getValue() != null) {
    
    
                    if (isFirst) {
    
    
                        isFirst = false;
                    } else {
    
    
                        strBuilder.append("&");
                    }
                    strBuilder.append(CharSequenceUtil.toUnderlineCase(entry.getKey())).append("=").append(Convert.toStr(entry.getValue()));
                }
            }
        }
        return strBuilder.toString();
    }

    @Override
    public int getOrder() {
    
    
        return order;
    }

}

原以为将json请求在网关层替换为application/x-www-form-urlencoded格式，并将参数转换key=value&key1=value1形式，拼接最后的请求地址
http://localhost:8010/oauth/token?key=value&key1=value1，这样就可以生效了，但测试后会报：java.lang.IllegalStateException: completed 错误

Filter RouteLocator 路由跳转形式(无效)

@Configuration
public class FilterConfig {
    
    

    @Bean
    public RouteLocator routes(RouteLocatorBuilder builder, ObjectMapper objectMapper) {
    
    
        return builder
                .routes()
                .route("path_route_change",
                        r -> r.path("/oauth/token")
                                .filters(f -> f
                                        .modifyRequestBody(String.class,String.class,"application/x-www-form-urlencoded",new RequestBodyRewrite(objectMapper))
                                )
                                .uri("http://localhost:8010/oauth/token"))
                .build();
    }
}

stackoverflow 提供的方式（无效）

这种办法根本不进Filter，在独立应用的时候也测试了
可见地址：https://stackoverflow.com/questions/38165131/spring-security-oauth2-accept-json

包装 oauth/token接口（有效）

	@PostMapping("oauth/api/token")
	public OAuth2AccessToken getToken(@Valid @RequestBody AuthTokenReq authTokenReq) {
    
    
		Map<String, String> params = new HashMap<>();
		params.put("grant_type", authTokenReq.getGrantType());
		params.put("client_id", authTokenReq.getClientId());
		params.put("client_secret", authTokenReq.getClientSecret());

		UsernamePasswordAuthenticationToken usernamePasswordAuthenticationToken = new UsernamePasswordAuthenticationToken(authTokenReq.getClientId(), authTokenReq.getClientSecret(), new ArrayList<>());

		ResponseEntity<OAuth2AccessToken> oAuth2AccessToken = tokenEndpoint.postAccessToken(usernamePasswordAuthenticationToken, params);

		return oAuth2AccessToken.getBody();
	}

新写一个REST接口，调用TokenEndpoint 的postAccessToken方法，还是这种办法最简单有效。

这里我通过TokenEndpoint 直接调用了postAccessToken方法，而不是采用Http请求oauth/token再次自我请求的方式，这种方式显得更优雅，性能也更高。