Spring @RestController 不返回纯文本响应

使用Spring框架构建RESTful API是开发者常用的方式之一。在Spring中，我们可以使用@RestController注解来标记一个类，使其成为一个RESTful API的控制器。这样，我们就可以方便地处理HTTP请求，并返回相应的响应。然而，默认情况下，@RestController注解返回的是JSON格式的数据，而不是纯文本响应。那么，如果我们想要返回纯文本响应怎么办呢？本文将介绍如何在Spring中实现这一需求，并给出相应的案例代码。

java
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotWritableException;
import java.io.IOException;
import java.nio.charset.Charset;
import java.util.Arrays;
import java.util.List;
public class TextPlainHttpMessageConverter implements HttpMessageConverter {
    @Override
    public boolean canRead(Class clazz, MediaType mediaType) {
        return false;
    }
    @Override
    public boolean canWrite(Class clazz, MediaType mediaType) {
        return mediaType != null && mediaType.isCompatibleWith(MediaType.TEXT_PLAIN);
    }
    @Override
    public List getSupportedMediaTypes() {
        return Arrays.asList(MediaType.TEXT_PLAIN, MediaType.ALL);
    }
    @Override
    public String read(Class clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException {
        throw new UnsupportedOperationException("TextPlainHttpMessageConverter does not support reading.");
    }
    @Override
    public void write(String s, MediaType contentType, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException {
        if (contentType == null) {
            contentType = MediaType.TEXT_PLAIN;
        }
        HttpHeaders headers = outputMessage.getHeaders();
        headers.setContentType(contentType);
        Charset charset = Charset.forName("UTF-8");
        headers.setAcceptCharset(Arrays.asList(charset));
        outputMessage.getBody().write(s.getBytes(charset));
    }
}

java
@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
    @Override
    public void configureMessageConverters(List> converters) {
        converters.add(new TextPlainHttpMessageConverter());
    }
}

java
@RestController
public class MyController {
    @GetMapping("/text")
    public String getText() {
        return "This is a text response!";
    }
}