Spring Boot @RequestBody如何接收非JSON格式字符串参数？

spring:
  jackson:
    parser:
      disable-unwrapped-values: true

@postmapping(value = "/sendnews", consumes = "text/plain")
public string sendcontent(string lstmsgid) {
    // ...
}

// 自定义非JSON字符串转换器
public class PlainStringHttpMessageConverter implements HttpMessageConverter<String> {

    @Override
    public boolean canRead(Class<?> clazz, MediaType mediaType) {
        return String.class.equals(clazz) && !mediaType.includes(MediaType.APPLICATION_JSON);
    }

    @Override
    public boolean canWrite(Class<?> clazz, MediaType mediaType) {
        return false;
    }

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

    @Override
    public String read(String cls, HttpInputMessage inputMessage) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(inputMessage.getBody()));
        return reader.readLine();
    }

    @Override
    public void write(String t, MediaType contentType, HttpOutputMessage outputMessage) {
        throw new UnsupportedOperationException();
    }
}

// 注册转换器
public class WebMvcConfig implements WebMvcConfigurer {

    @Override
    public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
        converters.add(new PlainStringHttpMessageConverter());
    }
}