The specified Tomcat installation directory does not exist

If you encountered this error on Eclipse:

The specified Tomcat installation directory does not exist.

Check for CATALINA_HOME value on commandline. Type set on commandline, you can then see the value of CATALINA_HOME, mine is /Library/Tomcat/Home

Go to Eclipse's Preferences. Go to Server > Runtime Environments. Then click Add, then select Apache Tomcat, click Next; on Tomcat installation directory, click Browse..., then paste /Library/Tomcat/Home to the Open dialog textbox; if you are using OS X press command+shift+G first, then paste /Library/Tomcat/Home in the Go to the folder's textbox, then click Go, then click Open

Then click Finish, then click OK

You can now create Dynamic Web Project

NOTE: a missing vtable usually means the first non-inline virtual member function has no definition

When you encounter this compilation error:

Michael-Buens-MacBook:CppProj Michael$ gcc b.cpp
Undefined symbols for architecture x86_64:
  "operator new(unsigned long)", referenced from:
      _main in ccbv8mjf.o
      Alpha::doStuff(char) in ccbv8mjf.o
      Beta::doStuff(char) in ccbv8mjf.o
  "vtable for __cxxabiv1::__class_type_info", referenced from:
      typeinfo for Alphain ccbv8mjf.o
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
  "vtable for __cxxabiv1::__si_class_type_info", referenced from:
      typeinfo for Betain ccbv8mjf.o
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status

You are holding it wrong, use g++ :-)

Michael-Buens-MacBook:CppProj Michael$ g++ b.cpp

b.cpp (Liskov principle):

#include <cstdio>

class Alpha
{
 public: virtual Alpha* doStuff(char c)
 {
  printf("From Alpha\n");
  return new Alpha();
 }
};

class Beta : public Alpha
{
 public: virtual Beta* doStuff(char c)
 {
  printf("From Beta\n");
  return new Beta();
 }
};

int main()
{

 Alpha* a = new Beta();
 Alpha* x = a->doStuff('x');
 
 Beta* b = new Beta();
 Beta* y = b->doStuff('x'); // no need to cast to Beta
 
 
 return 0;
}

Hibernate Troubleshooting

If you have the following errors, just drag the jar file to your lib folder

java.lang.NoClassDefFoundError: org/dom4j/DocumentException

copy this to your lib: dom4j-1.6.1.jar

java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory

copy this to your lib: slf4j-api-1.6.1.jar

java.lang.NoClassDefFoundError: javax/persistence/EntityListeners

copy this to your lib: hibernate-jpa-2.0-api-1.0.0.Final.jar

org.hibernate.HibernateException: JDBC Driver class not found: org.postgresql.Driver

copy this to your lib: postgresql-9.0-801.jdbc4.jar
download the latest Postgresql jdbc jar file from postgresql.org

java.lang.NoClassDefFoundError: org/apache/commons/collections/map/LRUMap

copy this to your lib: commons-collections-3.1.jar

org.hibernate.HibernateException: Unable to instantiate default tuplizer [org.hibernate.tuple.entity.PojoEntityTuplizer]

copy this to your lib: javassist-3.12.0.GA.jar

java.lang.NoClassDefFoundError: javax/transaction/Synchronization

copy this to your lib: jta-1.1.jar