private Map<String, String> decodeJsonTypes(Map<String, String> source) {
		if (source.containsKey(JSON_TYPES)) {
			String value = source.get(JSON_TYPES);
			try {
				return objectMapper.readValue(value,
						new TypeReference<Map<String, String>>() {
						});
			}
			catch (IOException e) {
				log.error("Could not decode json types: " + value, e);
			}
		}
		return Collections.emptyMap();
	}
Add packages to the trusted packages list (default {@code java.util, java.lang})
used when constructing objects from JSON. If any of the supplied packages is
{@code "*"}, all packages are trusted. If a class for a non-trusted package is
encountered, the header is returned to the application with value of type
{@link NonTrustedHeaderType}.
@param packagesToTrust the packages to trust.
spring-cloud-alibaba-starters/spring-cloud-starter-stream-rocketmq/src/main/java/com/alibaba/cloud/stream/binder/rocketmq/support/JacksonRocketMQHeaderMapper.java