content: package com.alibaba.fastjson2.support.spring.codec;
  
  import com.alibaba.fastjson2.JSON;
  import com.alibaba.fastjson2.JSONException;
  import com.alibaba.fastjson2.support.config.FastJsonConfig;
  import org.reactivestreams.Publisher;
  import org.springframework.core.ResolvableType;
  import org.springframework.core.codec.AbstractDecoder;
  import org.springframework.core.codec.DecodingException;
  import org.springframework.core.codec.Hints;
  import org.springframework.core.io.buffer.DataBuffer;
  import org.springframework.core.io.buffer.DataBufferUtils;
  import org.springframework.core.log.LogFormatUtils;
  import org.springframework.http.MediaType;
  import org.springframework.lang.NonNull;
  import org.springframework.lang.Nullable;
  import org.springframework.util.MimeType;
  import reactor.core.publisher.Flux;
  import reactor.core.publisher.Mono;
  
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.util.Map;
  
  /**
   * spring message codec decoder for Fastjson2.
   *
   * @author 张治保
   * @since 2025/8/6
   */
  public final class Fastjson2Decoder
          extends AbstractDecoder<Object> {
      private final FastJsonConfig config;
  
      /**
       * default constructor
       */
      public Fastjson2Decoder() {
          this(new FastJsonConfig(), MediaType.APPLICATION_JSON, new MediaType("application", "*+json"));
      }
  
      /**
       * Constructor with custom configs
       *
       * @param config    FastJsonConfig
       * @param mimeTypes the mime types to support
       */
      public Fastjson2Decoder(FastJsonConfig config, MimeType... mimeTypes) {
          super(mimeTypes == null || mimeTypes.length == 0
                  ? new MimeType[]{MediaType.APPLICATION_JSON, new MediaType("application", "*+json")}
                  : mimeTypes);
          this.config = config;
      }
  
      @Override
      @NonNull
      public Flux<Object> decode(@NonNull Publisher<DataBuffer> inputStream, @NonNull ResolvableType elementType, @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
          return Flux.from(inputStream)
                  .mapNotNull(dataBuffer -> decode(dataBuffer, elementType, mimeType, hints));
      }
  
      @Override
      @Nullable
      public Object decode(@NonNull DataBuffer buffer, @NonNull ResolvableType targetType, MimeType mimeType, Map<String, Object> hints) throws DecodingException {
          try (ByteArrayOutputStream os = new ByteArrayOutputStream();
                  InputStream in = buffer.asInputStream()) {
              byte[] buf = new byte[1 << 16];
              for (; ; ) {
                  int len = in.read(buf);
                  if (len == -1) {
                      break;
                  }
                  if (len > 0) {
                      os.write(buf, 0, len);
                  }
              }
              Object value = JSON.parseObject(os.toByteArray(),
                      targetType.getType(),
                      this.config.getDateFormat(),
                      this.config.getReaderFilters(),
                      this.config.getReaderFeatures());
              logValue(value, hints);
              return value;
          } catch (JSONException ex) {
              throw new DecodingException("JSON parse error: " + ex.getMessage(), ex);
          } catch (IOException ex) {
              throw new DecodingException("I/O error while reading input message", ex);
          } finally {
              DataBufferUtils.release(buffer);
          }
      }
  
      @Override
      @NonNull
      public Mono<Object> decodeToMono(@NonNull Publisher<DataBuffer> inputStream, @NonNull ResolvableType elementType,
                                       @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
          return DataBufferUtils.join(inputStream)
                  .flatMap(dataBuffer -> Mono.justOrEmpty(decode(dataBuffer, elementType, mimeType, hints)));
      }
  
      private void logValue(@Nullable Object value, @Nullable Map<String, Object> hints) {
          if (!Hints.isLoggingSuppressed(hints)) {
              LogFormatUtils.traceDebug(logger, traceOn -> {
                  String formatted = LogFormatUtils.formatValue(value, !traceOn);
                  return Hints.getLogPrefix(hints) + "Decoded [" + formatted + "]";
              });
          }
      }
  }
  