Read the Error Message - Problem Solving Skills

The first step of trouble shooting is to read and understand the error message, then we can infer,guess and list likely causes from it, verify or exclude it one by one.

Senario 1
After upgrade some library to newer version and upgrade to JDK 8 and tomcat 8, deployment of the web application fails.

Step 1: Read/Understand the error message
SEVERE [localhost-startStop-1] org.apache.catalina.core.ContainerBase.addChildInternal ContainerBase.addChild: start:
 org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/webappA]]
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
        at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:725)
        at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:701)
        at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717)
        at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:945)
        at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1798)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalStateException: Unable to complete the scan for annotations for web application [/webappA] due to a StackOverflowError. Possible root causes include a too low setting for -Xss and illegal cyclic inheritance dependencies. The class hierarchy being processed was [org.bouncycastle.asn1.ASN1Boolean->org.bouncycastle.asn1.DERBoolean->org.bouncycastle.asn1.ASN1Boolean]
        at org.apache.catalina.startup.ContextConfig.checkHandlesTypes(ContextConfig.java:2066)
        at org.apache.catalina.startup.ContextConfig.processAnnotationsStream(ContextConfig.java:2012)
        at org.apache.catalina.startup.ContextConfig.processAnnotationsJar(ContextConfig.java:1961)
        at org.apache.catalina.startup.ContextConfig.processAnnotationsUrl(ContextConfig.java:1936)
        at org.apache.catalina.startup.ContextConfig.processAnnotations(ContextConfig.java:1897)
        at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1149)
        at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:771)
        at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:305)
        at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:95)
        at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
        at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5080)
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
        ... 10 more
In another app, the error message is:
Caused by: java.lang.IllegalStateException: Unable to complete the scan for annotations for web application [/megaphone-admin-1.0.3_jbuild363] due to a StackOverflowError. Possible root causes include a too low setting for -Xss and illegal cyclic inheritance dependencies. The class hierarchy being processed was [org.bouncycastle.asn1.ASN1EncodableVector->org.bouncycastle.asn1.DEREncodableVector->org.bouncycastle.asn1.ASN1EncodableVector]

Step 2: Find which jar contains the class
org.bouncycastle.asn1.DERBoolean
http://www.findjar.com/class/org/bouncycastle/asn1/DERBoolean.html

ls -altr | grep bcprov
-rw-r--r-- 1 tomcat tomcat  2902942 Sep 25 22:01 bcprov-jdk15on-1.52.jar
-rw-r--r-- 1 tomcat tomcat  1876535 Oct 12 07:01 bcprov-jdk16-1.46.jar
-rw-r--r-- 1 tomcat tomcat  1593423 Oct 12 07:01 bcprov-jdk15-140.jar

run mvn dependency:tree and check why these jars are imported, and use dependency/exclusion to exclude the old ones.

<exclusion>
  <groupId>org.bouncycastle</groupId>
  <artifactId>bcmail-jdk15on</artifactId>
</exclusion>
<exclusion>
  <groupId>org.bouncycastle</groupId>
  <artifactId>bcprov-jdk15on</artifactId>
</exclusion>

Senario 2
When deploy the app to jdk8, it fails:
org.aspectj.apache.bcel.classfile.ClassFormatException: Invalid byte tag in constant pool: 18.

To fix it, I need upgrade aspectj related libs to latest one 1.8.9 - exclude from the framework that imported it, and explicitly declare them to use 1.8.9.

Then when I run mvn clean install, it fails:  
The following artifacts could not be resolved: aspectjrt:org.aspectj:jar:1.8.9, aspectjweaver:org.aspectj:jar:1.8.9

It took me one hour and finally realized that I made a stupid mistake: I typed artifactId where it should be groupid.
<exclusion>
  <artifactId>org.aspectj</artifactId>
  <groupId>aspectjrt</groupId>
</exclusion>

If I can check the error message more carefully and think about the possible causes, it would save me a hour.

Senario 3
Error creating bean with name 'org.springframework.security.config.authentication.AuthenticationManagerFactoryBean#0'
I converted the xml declaration of authentication-manager to java config bean, it failed with above error.

There are a lot of error messages(200+ lines), but as long as I scan all error messages, the root cause is clear:
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.security.authenticationManager' defined in class path resource WebSecurityConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.security.authentication.AuthenticationManager]: Factory method 'authenticationManager' threw exception; nested exception is java.lang.IllegalArgumentException: A parent AuthenticationManager or a list of AuthenticationProviders is required
....
Caused by: java.lang.IllegalArgumentException: A parent AuthenticationManager or a list of AuthenticationProviders is required
at org.springframework.security.authentication.ProviderManager.checkState(ProviderManager.java:117) ~[spring-security-core-3.2.5.RELEASE.jar:3.2.5.RELEASE]
at org.springframework.security.authentication.ProviderManager.<init>(ProviderManager.java:106) ~[spring-security-core-3.2.5.RELEASE.jar:3.2.5.RELEASE]
at org.springframework.security.authentication.ProviderManager.<init>(ProviderManager.java:99) ~[spring-security-core-3.2.5.RELEASE.jar:3.2.5.RELEASE]

at xx.services.app.config.WebSecurityConfiguration.authenticationManager(WebSecurityConfiguration.java:33) ~[WebSecurityConfiguration.class:na]

This is because of the bug in the code: I first create an empty list then create authenticationManager with the empty list.
@Bean
public AuthenticationManager authenticationManager() {
    final List<AuthenticationProvider> providers = new ArrayList<>();
    // this will fail: we have to first add providers to the list then create authenticationManager with the non-empty provider list.
    final AuthenticationManager authenticationManager = new ProviderManager(providers);
    ...// build daoAuthenticationProvider, ldapAuthenticationProvider
    providers.add(daoAuthenticationProvider);
    providers.add(ldapAuthenticationProvider);
}