requestresearch.java

来自「100多M的J2EE培训内容」· Java 代码 · 共 209 行

package bible.ejb.session.example1;



import java.rmi.*;

import javax.ejb.*;

import java.util.*;

import javax.naming.*;


/**
 * Class RequestResearch
 *
 *
 * @author
 * @version %I%, %G%
 */
public class RequestResearch implements SessionBean {

  // Implemented create method required by RequestResearchHome.

  /**
   * Method ejbCreate
   *
   *
   */
  public void ejbCreate() {}

  // Implemented methods required by SessionBean.
  private SessionContext sessionContext;

  /**
   * Method ejbRemove
   *
   *
   * @throws RemoteException
   *
   */
  public void ejbRemove() throws RemoteException {}

  /**
   * Method ejbActivate
   *
   *
   * @throws RemoteException
   *
   */
  public void ejbActivate() throws RemoteException {}

  /**
   * Method ejbPassivate
   *
   *
   * @throws RemoteException
   *
   */
  public void ejbPassivate() throws RemoteException {}

  /**
   * Method setSessionContext
   *
   *
   * @param sessionContext
   *
   * @throws RemoteException
   *
   */
  public void setSessionContext(SessionContext sessionContext)
    throws RemoteException {
    this.sessionContext = sessionContext;
  }

  // Methods for processing requests for research as required
  // for the RequestResearchRemote interface.

  /**
   * Fetches and returns research for a security.
   */
  public String requestResearch(String symbol) throws RemoteException {

    // CheckEnvironment flag here to see whether to route the call to the
    // internal system.
    String research = null;

    if (this.useRequestDataManager()) {
      System.out.println("Locally calling RequestDataManager for research.");

      research = getResearchFromDataManager(symbol);
    } else {
      System.out.println("Randomly generating research for this symbol.");

      research = createRandomResearch(symbol);
    }

    return research;
  }

  /**
   * Randomly creates 'research' for this security.
   */
  private String createRandomResearch(String symbol) {

    Random rand = new Random();
    int    x    = rand.nextInt();

    x = x % 3;

    String research = null;

    switch (x) {

    case 0 :
      research = "Zeetrade recommends you buy " + symbol;
      break;

    case 1 :
      research = "Zeetrade recommends you hold " + symbol;
      break;

    default :
      research = "Zeetrade recommends you sell " + symbol;
      break;
    }

    return research;
  }

  /**
   * Does an environment entry lookup to determine where or not to use
   * the DataManager or randomly generate data here.  This field can be edited in
   * the ejb-jar.xml before EJB deployment.
   */
  private boolean useRequestDataManager() {

    System.out.println("Checking the env-entry for useRequestDataManager");

    InitialContext ctx        = null;
    boolean        useManager = false;

    try {

      // Because Request Research is a bean living in the EJB container,
      // no need to specify server parameters to obtain the correct context.
      ctx = new InitialContext();

      Boolean useManagerBool =
        (Boolean) ctx.lookup("java:comp/env/useRequestDataManager");

      useManager = useManagerBool.booleanValue();
    } catch (Exception e) {
      e.printStackTrace();
    } finally {
      try {
        ctx.close();
      } catch (Exception e) {}
    }

    return useManager;
  }

  /**
   * Calls local EJB RequestDataManager to get research.
   */
  private String getResearchFromDataManager(String symbol) {

    InitialContext ctx = null;
    StringBuffer   sb  = new StringBuffer();

    try {

      // Because Request Research is a bean living in the EJB container,
      // no need to specify server parameters to obtain the correct context.
      ctx = new InitialContext();

      Object objref = ctx.lookup("RequestDataManager");

      // No need to do narrow, simply cast as this is a local object to this JVM.
      RequestDataManagerLocalHome home     =
        (RequestDataManagerLocalHome) objref;
      RequestDataManagerLocal     dataBean = home.create();

      sb.append("**Data Retreived from the local datasource**");

      // Call the dataBean, this is not pass by value as in RMI (Remote
      // beans included) Instead the stringbuffer is passed by reference,
      // and therefore when the local session EJB RequestDataManager
      // appends to it, the appends are altering this buffer (sb).
      dataBean.appendResearchData(sb, symbol);
    } catch (Exception e) {
      e.printStackTrace();
    } finally {
      try {
        ctx.close();
      } catch (Exception e) {}
    }

    return sb.toString();
  }
}


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