9.3.3 How to reference exceptions on OTM clients

(a) Overview of exception structures

Restrictions placed on an OTM client include inabilities to interpret data that has a recursive structure and to use valuetype. Therefore, an exception thrown by an EJB application is converted into an exception that has a structure as a member as shown in the following figure. This structure is called an exception structure.

Figure 9‒2: Exception class and exception structure

An exception is converted into an exception structure, and then the OTM client catches an exception that has the exception structure as a member. When a user throws a MsgServerException exception from an EJB application, the OTM client catches the exception as a MsgServerEx exception. The value member of the MsgServerEx exception is the MsgServerException exception structure.

Figure 9‒3: Retrieving an exception structure from an exception class

(b) Member of an exception structure

The following table describes the members contained in an exception structure.

Table 9‒7: Members of an exception structure

No.	Structure member	Contents
1	order	OTM application developers do not need to use these items. These items are required for the OTM client to receive the structure as an exception.
2	count
3	cause	OTM application developers do not need to use these items. On the OTM client, do not throw an exception from the EJB application by setting any value in cause.
4	detailMessage	Detail message specified in the super class
5	stackTrace	Stack trace up to the time when an exception is generated on the EJB application side
6	Member variables	Member variables set in a Java user-defined exception. For RemoteException, no member variables exist.

(c) Information items of a stack trace

The stackTrace member of an exception structure is an array for the StackTraceElement structure. The StackTraceElement structure contains a single stack of stack traces.

The following table shows the information set in each member of the StackTraceElement structure.

Table 9‒8: Members of the StackTraceElement structure

No.	Field name	Contents	Example
1	LineNumber	Source line number	29
2	declaringClass	Class name	jp.co.Hitachi.soft.test.ejb.testMsgSyncServiceDelEJB
3	FileName	File name	testMsgSyncServiceDelEJB.java
4	MethodName	Method name	InvokeBinary

Package jp.co.Hitachi.soft.test;
public class MsgServerException extends Exception
{
    public MsgServerException()
    {
      m_case=1;
    }
    private int m_case;
}

(a) Example of referencing exception information with C++

The following shows an example of referencing exception information with C++ code:

#define ERR_FORMAT "EC=%d,DC=%d,PC=%d,CS=%d,MC1=%d,MC2=%d,MC3=%d,MC4=%d\n"
// Function that returns the length of the specified string
int my_wstringlen(CORBA::WChar* arg){
    int i;
    for(i=0;arg[i] != 0;i++);
    return i;
}
// Function that displays the specified string
void my_print_wstring(CORBA::WChar* arg){
    for(int i=0;i < my_wstringlen(arg); i++){
      printf("%c", arg[i]);
    }
}
 
int main(int argc, char** argv){
  try {
      // Processing to invoke the EJB application (omitted)
  }catch(jp::co::Hitachi::soft::test::MsgServerEx &e){
   // EJB application throws a Java user-defined exception (MsgServerException)
    jp::co::Hitachi::soft::test::CSCMsgServerException& ex_val = e.value;
 
    // Output a detail message
    printf("detailMessage:");
    ::TSC::TSCWStringValue& detailMessage = ex_val.detailMessage;
    CORBA::WChar* w_detail_msg = new CORBA::WChar[detailMessage.value.length()];
    w_detail_msg = TSCgetWString(detailMessage.value );
    my_print_wstring(w_detail_msg);
    printf("\n");
 
    // Output the m_case member variable
    printf("m_case:%d", ex_val.m_case);
    // Output a stack trace
    ::TSC::java::lang::seq1_StackTraceElement& stackTrace = ex_val.stackTrace;
    CORBA::ULong len = stackTrace.value.length();
    :TSC::java::lang::StackTraceElement stackTraceElement;
    for ( int i = 0 ; i < len ; i ++ ) {
        stackTraceElement = stackTrace.value [ i ] ;
        ::TSC::TSCWStringValue& className = stackTraceElement.declaringClass;
        ::TSC::TSCWStringValue& methodName= stackTraceElement.methodName;
        ::TSC::TSCWStringValue& fileName = stackTraceElement.fileName;
        CORBA::Long lineNumber= stackTraceElement.lineNumber;
 
        CORBA::WChar* w_class_name = new CORBA::WChar[className.value.length()];
        w_class_name = TSCgetWString( className.value );
 
      CORBA::WChar* w_method_name = new CORBA::WChar[methodName.value.length()];
      w_method_name = TSCgetWString( methodName.value );
 
      CORBA::WChar* w_file_name = new CORBA::WChar[fileName.value.length()];
      w_file_name = TSCgetWString( fileName.value );
 
      printf("at ");
      my_print_wstring(w_class_name);
      printf(".");
      my_print_wstring(w_method_name);
      printf("(");
      my_print_wstring(w_file_name);
      printf(":%d)\n",lineNumber);
    }
}catch(TSC::java::rmi::RemoteEx &e){
    // EJB application throws a Java runtime exception
    // EJB application throws a Java system-defined error
    // EJB application throws a java.rmi.RemoteException
 
    TSC::java::rmi::RemoteException& ex_val = e.value;
 
    // Output a detail message
    printf("detailMessage:");
    ::TSC::TSCWStringValue& detailMessage = ex_val.detailMessage;
    CORBA::WChar* w_detail_msg = new CORBA::WChar[detailMessage.value.length()];
    w_detail_msg = TSCgetWString(detailMessage.value );
    my_print_wstring(w_detail_msg);
    printf("\n");
 
    // Output a stack trace
    ::TSC::java::lang::seq1_StackTraceElement& stackTrace = ex_val.stackTrace;
    CORBA::ULong len = stackTrace.value.length();
    :TSC::java::lang::StackTraceElement stackTraceElement;
    for ( int i = 0 ; i < len ; i ++ ) {
        stackTraceElement = stackTrace.value [ i ] ;
        ::TSC::TSCWStringValue& className = stackTraceElement.declaringClass;
        ::TSC::TSCWStringValue& methodName= stackTraceElement.methodName;
        ::TSC::TSCWStringValue& fileName = stackTraceElement.fileName;
        CORBA::Long lineNumber= stackTraceElement.lineNumber;
 
        CORBA::WChar* w_class_name = new CORBA::WChar[className.value.length()];
        w_class_name = TSCgetWString( className.value );
      CORBA::WChar* w_method_name = new CORBA::WChar[methodName.value.length()];
      w_method_name = TSCgetWString( methodName.value );
 
      CORBA::WChar* w_file_name = new CORBA::WChar[fileName.value.length()];
      w_file_name = TSCgetWString( fileName.value );
 
      printf("at ");
      my_print_wstring(w_class_name);
      printf(".");
      my_print_wstring(w_method_name);
      printf("(");
      my_print_wstring(w_file_name);
      printf(":%d)\n",lineNumber);
    }
} catch(TSCSystemException& se) {
    // EJB application throws a Java system-defined error
    // EJB application throws a CORBA system exception
    // Invocation of the EJB application fails
    printf(ERR_FORMAT,
            se.getErrorCode(), se.getDetailCode(),
            se.getPlaceCode(), se.getCompletionStatus(),
            se.getMaintenanceCode1(), se.getMaintenanceCode2(),
            se.getMaintenanceCode3(), se.getMaintenanceCode4());
} catch(UserExcept& se) {
    // EJB application throws a CORBA user exception
    printf("UserExcept\n");
}

(b) Example of referencing exception information with Java

The following shows an example of referencing exception information with Java code.

// Function that performs byte[]-to-char[] conversion to obtain String
private static String myString(byte[] barray) {
    char[] carry = new char[barray.length/2];
    for ( int i=0;i<carry.length;i++) {
        carry[i] = (char)((( barray[i*2]& 0xff) << 8 ) | barray[(i*2)+1]& 0xff) ;
    }
    return new String(carry);
}
 
public static void main(String[] args) {
  try {
      // Processing to invoke an EJB application (omitted)
  }catch(jp.co.Hitachi.soft.test.MsgServerEx ex) {
 
     // EJB application throws a Java user-defined exception (MsgServerException)
    jp.co.Hitachi.soft.csc.msg.message.reception.MsgServerException testException = ex.value;
 
    // Output a detail message
    System.out.println ("detailMessage:"+ myString(testException.detailMessage);
 
    // Output the m_case member variable
    System.out.println ("m_case:%d"+ testException .m_case);
 
    // Output a stack trace
    TSC.java.lang.StackTraceElement[] stackElements= testException.stackTrace.value;
    java.lang.StringBuffer stb = new java.lang.StringBuffer();
 
    for (int i=0;i<stackElements.length;i++) {
        stb = stb.append("at ");
        stb = stb.append(myString(stackElements[i].declaringClass.value));
        stb = stb.append(".");
        stb = stb.append(myString(stackElements[i].methodName.value));
        stb = stb.append("(");
        stb = stb.append(myString(stackElements[i].fileName.value));
        stb = stb.append(":");
        stb = stb.append(stackElements[i].lineNumber);
        stb = stb.append(")");
        stb = stb.append("\n");
    }
        System.out.println(stb.toString());
}catch(TSC.java.rmi.RemoteEx ex) {
    // EJB application throws a Java runtime exception
    // EJB application throws a Java system-defined error
    // EJB application throws a java.rmi.RemoteException
    TSC.java.rmi.RemoteException testException = ex.value;
 
    // Output a detail message
    System.out.println ("detailMessage:"+ myString(testException.detailMessage);
    // Output a stack trace
    TSC.java.lang.StackTraceElement[] stackElements= testException.stackTrace.value;
    java.lang.StringBuffer stb = new java.lang.StringBuffer();
 
    for (int i=0;i<stackElements.length;i++) {
        stb = stb.append("at ");
        stb = stb.append(myString(stackElements[i].declaringClass.value));
        stb = stb.append(".");
        stb = stb.append(myString(stackElements[i].methodName.value));
        stb = stb.append("(");
        stb = stb.append(myString(stackElements[i].fileName.value));
        stb = stb.append(":");
        stb = stb.append(stackElements[i].lineNumber);
        stb = stb.append(")");
        stb = stb.append("\n");
    }
        System.out.println(stb.toString());
} catch(TSCSystemException tsc_se) {
    // EJB application throws a Java system-defined exception
    // EJB application throws a CORBA system exception
    // Invocation of the EJB application fails
    System.out.println(tsc_se);
} catch(UserExcept tsc_se) {
    // EJB application throws a CORBA user exception
    System.out.println("catch" + tsc_se.value);
}