[Q/A][Java SDK (Component)] dubbo upgrade 3.0.10->3.2.16, occurred NPE ?

[uzong]

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Apache Dubbo Component

Java SDK (apache/dubbo)

Details

"2025-02-13 09:21:38.389  INFO 1 --- [           main] [] [] .r.c.e.l.ServiceInstancesChangedListener :  [DUBBO] Notify serviceKey: com.xxx.xxx.api.xxxService:null, listener: ServiceDiscoveryRegistryDirectory(registry: nacos.dev:8848, subscribed key: [xxx-xxx, xxx-xxx-felix])-Directory(invokers: 0[], validInvokers: 0[], invokersToReconnect: 0[]) with 1 urls on subscription, dubbo version: 3.2.16, current host: 10.0.3.248

25-02-13 09:21:38.390 ERROR 1 --- [           main] [] [] .d.r.c.ServiceDiscoveryRegistryDirectory :  [DUBBO] Failed to refer invoker for interface:interface com.xxx.xxx.api.xxxService,url:(DefaultServiceInstance{serviceName='xxx-xxx', host='10.0.4.55', port=20880, enabled=true, healthy=true, metadata={dubbo.endpoints=[{"port":8100,"protocol":"rest"},{"port":20880,"protocol":"dubbo"}], dubbo.metadata.revision=64bfa545c732b6216157459eea6b8db3, dubbo.metadata.storage-type=remote, timestamp=1739329059522}}, service{name='com.xxx.xxx.api.xxxService',group='null',version='null',protocol='dubbo',port='-1',params=null,})null, dubbo version: 3.2.16, current host: 10.0.3.248, error code: 4-3. This may be caused by , go to https://dubbo.apache.org/faq/4/3 to find instructions. 
java.lang.NullPointerException: null
	at org.apache.dubbo.metadata.MetadataInfo$ServiceInfo.getParameter(MetadataInfo.java:747)
	at org.apache.dubbo.metadata.MetadataInfo.getParameter(MetadataInfo.java:290)
	at org.apache.dubbo.registry.client.InstanceAddressURL.getServiceParameter(InstanceAddressURL.java:264)
	at org.apache.dubbo.registry.client.InstanceAddressURL.getParameter(InstanceAddressURL.java:236)
	at org.apache.dubbo.common.URL.hasParameter(URL.java:807)
	at org.apache.dubbo.registry.client.ServiceDiscoveryRegistryDirectory.toInvokers
	.....

When I upgraded the dubbo version from 3.0.10 to 3.2.16, the above problem occurred. In the MetadataInfo$ServiceInfo.getParameter method, params was null.

org.apache.dubbo.metadata.MetadataInfo.ServiceInfo#getParameter

	public String getParameter(String key) {
	if (consumerParams != null) {
		String value = consumerParams.get(key);
		if (value != null) {
			return value;
		}
	}
	return params.get(key);
}

Thank God for helping me solve the problem

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[AlbumenJ]

Can you pls provide a demo to reproduce it?

[uzong]

I have solved it, it was an issue with fastjson2 that was not able to deserialize $ref\, causing the parameter to resolve to null, I have already ruled out the version of fastjson2 that was causing it.

===================== code ===================

public class Main {
    public static void main(String[] args) {
        MetadataInfoSimple javaObject = toJavaObject(json, MetadataInfoSimple.class);
        System.out.println(javaObject.getParams());
    }
    public static <T> T toJavaObject(String json, Type type) {
        return com.alibaba.fastjson2.JSON.parseObject(json, type);
    }

    private static String json = "{\n" +
            "   \n" +
            "      \"name\" : \"com.xxx.xxx.web.xxxEndPoint\",\n" +
            "      \"params\" : {\n" +
            "        \"$ref\" : \"$.services.com\\\\.xxx\\\\.xxx\\\\.web\\\\.xxxEndPoint\\\\:rest.allParams\"\n" +
            "      }\n" +
            "    }";

print null

===================== dubbo source code (3.2.16)===================

org.apache.dubbo.metadata.MetadataInfo.ServiceInfo#getParameter

public String getParameter(String key) {
    if (consumerParams != null) {
        String value = consumerParams.get(key);
        if (value != null) {
            return value;
        }
    }
// !!! NPE 
    return params.get(key);
}