记一次NoSuchMethodError问题的排查

现场描述

在升级了某组件后，应用启动时抛如下异常，导致启动失败：

2017-07-13 15:18:53.388 [C6686525] [] [] ERROR c.y.t.m.a.ServiceAspect - NoSuchMethodError
 Method:public com.youzan.api.common.response.PlainResult com.youzan.trade.manage.es.service.impl.SearchServiceImpl.getSearchResult(com.youzan.trade.man
age.api.param.SearchQueryParam)
 Arguments:{
}
java.lang.NoSuchMethodError: com.youzan.nsq.client.entity.NSQConfig.setLookupAddresses(Ljava/lang/String;)Lcom/youzan/nsq/client/entity/NSQConfig;
        at com.youzan.trade.metrics.NsqReporter.connect(NsqReporter.java:41) ~[trade-metrics-core-1.0-RELEASE.jar:na]
        at com.youzan.trade.metrics.NsqReporter.<init>(NsqReporter.java:36) ~[trade-metrics-core-1.0-RELEASE.jar:na]
        at com.youzan.trade.metrics.Registry.<init>(Registry.java:54) ~[trade-metrics-core-1.0-RELEASE.jar:na]

过程分析

工程A引入了组件甲、乙以及丙均依赖公司内二次开发NSQ-client，甲及乙为采集应用，均调用了NSQ-Client中NSQCongfig的同名方法，即上日志中提示NoSuchMethodError的方法：

config = new NSQConfig();
config.setLookupAddresses(lookUpAddress);

排查过程中，发现组件甲依赖的NSQ-Client版本为：2.2.20170424-RELEASE 乙依赖的NSQ-Client版本为2.3.20170424-RELEASE 粗对比两者的函数签名，方法名，入参都一致。百撕不得其姐。后 组内同学阿奎 debug的时候发现，两个版本的方法返回值不同，当时恍然大悟。自己在问题排查是并没有注意到返回值信息，因为在两个lib中调用时均未获取返回值，但是实际在编译过程中，已经将返回值信息编译到class文件中。
NSQ-Client两个版本相同类中对应方法签名分别为：

#2.3.20170424-RELEASE
public NSQConfig setLookupAddresses(final String lookupAddresses) 
#2.2.20170424-RELEASE
public void setLookupAddresses(String lookupAddresses) 

导致分别依赖两个版本NSQ-Client且均调用此方法的lib无法共存。

举一反三

public class NSQPublisher{
    private Client c = new Client();
    public void doSome(){
        c.command();
    }
    public static void main(String[] args){
        NSQPublisher publisher = new NSQPublisher();
        publisher.doSome();
    }
}
public class Client{
    public void command(){
        System.out.println("Do command");
    }
}

定义两个类，编译执行，正常输出：

➜  Desktop javac -cp . Client.java
➜  Desktop javac -cp . NSQPublisher.java
➜  Desktop java NSQPublisher
Do command

此时将Client中的command调整为返回boolean值，再编译执行，问题重现：

➜  Desktop javac -cp . Client.java
➜  Desktop java NSQPublisher
Exception in thread "main" java.lang.NoSuchMethodError: Client.command()V
    at NSQPublisher.doSome(NSQPublisher.java:5)
    at NSQPublisher.main(NSQPublisher.java:10)

直接查看反编译后信息：

➜  Desktop javap -c NSQPublisher.class
Compiled from "NSQPublisher.java"
public class NSQPublisher {
  public NSQPublisher();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."<init>":()V
       4: aload_0
       5: new           #2                  // class Client
       8: dup
       9: invokespecial #3                  // Method Client."<init>":()V
      12: putfield      #4                  // Field c:LClient;
      15: return
  public void doSome();
    Code:
       0: aload_0
       1: getfield      #4                  // Field c:LClient;
       4: invokevirtual #5                  // Method Client.command:()V
       7: return
  public static void main(java.lang.String[]);
    Code:
       0: new           #6                  // class NSQPublisher
       3: dup
       4: invokespecial #7                  // Method "<init>":()V
       7: astore_1
       8: aload_1
       9: invokevirtual #8                  // Method doSome:()V
      12: return
}

昭然若揭。