CORBA中傳遞對象 java語言

CORBA的IDL資料類型定義了一系列的基礎資料型別 (Elementary Data Type)，但是如果需要傳遞對象可能就有些問題了。雖然IDL檔案中的interface其實就是傳遞對象的一種方法，我的理解就是把要傳遞的對象的屬性分成基礎資料型別 (Elementary Data Type)傳遞過去，但是如果傳遞的對象結構變化了，還需要修改IDL檔案。所以想找到一個直接傳遞對象的方法，研究了CORBA定義的資料類型，最好的辦法就是像很多串連傳輸對象的方法一樣，傳遞byte數組。

建一個目錄，名為Hello（名字隨意起），然後在這個目錄中建兩個子目錄，分別為server，client

在兩個目錄中各建一個People.java檔案,內容如下:

import java.io.*;
class People implements Serializable
{
 private String name;
 private int age;

 public People()
 {
  name = "CY";
  age = 27;
 }

 public People(String str, int i)
 {
  name = str;
  age = i;
 }

 public String getName()
 {
  return name;
 }
 
 public int getAge()
 {
  return age;
 }

}

在server目錄建一個Hello.idl檔案,內容如下:

module HelloApp
{
  interface Hello
  {
  string sayHello();
  oneway void shutdown();
  };
};

同樣在server目錄建HelloServer.java檔案,內容如下:

// A server for the Hello object

import HelloApp.*;
import org.omg.CosNaming.*;
import org.omg.CosNaming.NamingContextPackage.*;
import org.omg.CORBA.*;
import org.omg.PortableServer.*;
import org.omg.PortableServer.POA;
import java.util.Properties;

public class HelloServer {

  public static void main(String args[]) {
    try{
      // create and initialize the ORB
      ORB orb = ORB.init(args, null);

      // get reference to rootpoa & activate the POAManager
      POA rootpoa =
        (POA)orb.resolve_initial_references("RootPOA");
      rootpoa.the_POAManager().activate();

      // create servant and register it with the ORB
      HelloImpl helloImpl = new HelloImpl();
      helloImpl.setORB(orb);

      // get object reference from the servant
      org.omg.CORBA.Object ref =
        rootpoa.servant_to_reference(helloImpl);

      // and cast the reference to a CORBA reference
      Hello href = HelloHelper.narrow(ref);
  
      // get the root naming context
      // NameService invokes the transient name service
      org.omg.CORBA.Object objRef =
          orb.resolve_initial_references("NameService");
      // Use NamingContextExt, which is part of the
      // Interoperable Naming Service (INS) specification.
      NamingContextExt ncRef =
        NamingContextExtHelper.narrow(objRef);

      // bind the Object Reference in Naming
      String name = "Hello1";
      NameComponent path[] = ncRef.to_name( name );
      ncRef.rebind(path, href);

      System.out.println
        ("HelloServer ready and waiting ...");

      // wait for invocations from clients
      orb.run();
    }
 
      catch (Exception e) {
        System.err.println("ERROR: " + e);
        e.printStackTrace(System.out);
      }
  
      System.out.println("HelloServer Exiting ...");
 
  } //end main
} // end class

在server目錄下建立HelloImpl.java檔案,內容如下:

// The servant -- object implementation -- for the Hello
// example.  Note that this is a subclass of HelloPOA, whose
// source file is generated from the compilation of
// Hello.idl using j2idl.

import HelloApp.*;
import org.omg.CosNaming.*;
import org.omg.CosNaming.NamingContextPackage.*;
import org.omg.CORBA.*;
import org.omg.PortableServer.*;
import org.omg.PortableServer.POA;

import java.util.Properties;
import java.io.*;

class HelloImpl extends HelloPOA //必須繼承這個類，在helloApp目錄中已自動產生
{
 private ORB orb;
  private byte[] bytes;
 public void setORB(ORB orb_val)
 {
  orb = orb_val;
 }

 // implement sayHello() method
 public byte[] sayHello()
 {
  return (ObjectToByte(new People("Chen Yi",27)));
 }

 // implement shutdown() method
 public void shutdown()
 {
  orb.shutdown(false);
 }
 public byte[] ObjectToByte(java.lang.Object obj)
 {

  try {
   //object to bytearray
   ByteArrayOutputStream bo = new ByteArrayOutputStream();
   ObjectOutputStream oo = new ObjectOutputStream(bo);
   oo.writeObject(obj);

   bytes = bo.toByteArray();

   bo.close();
   oo.close();

   
  }
  catch(Exception e) {
   System.out.println("translation"+e.getMessage());
   e.printStackTrace();
  }
  return(bytes);
 }

} //end class

在client目錄下建立HelloClient.java檔案,內容如下:

// A sample Java IDL object client application.
import HelloApp.*;
import org.omg.CosNaming.*;
import org.omg.CosNaming.NamingContextPackage.*;
import org.omg.CORBA.*;
import java.io.*;

public class HelloClient
{
 static Hello helloImpl;
 String [] x=new String[6];
 static People people;
 static java.lang.Object obj;
 public static void main(String args[]){
  try{
   // create and initialize the ORB
   ORB orb = ORB.init(args, null);

   System.out.println("ORB initialised/n");

   // get the root naming context
   org.omg.CORBA.Object objRef =
   orb.resolve_initial_references("NameService");

   // Use NamingContextExt instead of NamingContext,
   // part of the Interoperable naming Service.
   NamingContextExt ncRef =
   NamingContextExtHelper.narrow(objRef);

   // resolve the Object Reference in Naming
   String name = "Hello1";
   helloImpl =
   HelloHelper.narrow(ncRef.resolve_str(name));

      people = (People)(ByteToObject(helloImpl.sayHello()));

   System.out.println
   ("Obtained a handle on server object: "
   + helloImpl);
   System.out.println(people.getName());
   helloImpl.shutdown();

  }
  catch (Exception e) {
   System.out.println("ERROR : " + e) ;
   e.printStackTrace(System.out);
  }
 } //end main

 private static java.lang.Object ByteToObject(byte[] bytes){
  try {
  //bytearray to object
  ByteArrayInputStream bi = new ByteArrayInputStream(bytes);
  ObjectInputStream oi = new ObjectInputStream(bi);

  obj = oi.readObject();

  bi.close();
  oi.close();
  }
  catch(Exception e) {
   System.out.println("translation"+e.getMessage());
   e.printStackTrace();
  }
  return obj;
 }
} // end class

下面是單機版編譯步驟

1. 編譯server中IDL檔案,在命令列執行   idlj -fall HelloApp.idl

2. 編譯server中.java檔案  javac *.java

3. 將server中編譯IDL檔案後產生的檔案目錄HelloApp複製到client目錄中

4. 編譯client中.java檔案  javac *.java

5. 運行orbd  start orbd -ORBInitialPort 1050

6. 運行server  start java HelloServer -ORBInitialPort 1050 -ORBInitialHost localhost

7. 運行client  java HelloClient -ORBInitialPort 1050 -ORBInitialHost localhost

運行結果,會在client命令列中看到列印出人名.如果需要進一步測試,可以在HelloImpl中修改new People(str,i)的參數也可以在client中調用People的其他方法.

多機版運行方法
編譯方法同單機版
1. 運行orbd   start orbd -ORBInitialPort 1050 -ORBInitialHost servermachinename

2. 運行server   java HelloServer -ORBInitialPort 1050

3. 運行client   java HelloClient -ORBInitialHost nameserverhost -ORBInitialPort 1050

注意 nameserverhost 是伺服器的IP地址

另外idlj命令的參數也可以修改, -fall是產生server和client的映射, -fserver是產生server映射, -fclient是產生client映射.如果用後面兩個參數需要將.idl檔案分別放在兩個目錄中