本示例是在Weblogic的示范example中进行修改的,模拟Trade的buy和sell的过程.
定义了四个Business方法,具体看Remote接口Trader.
另外定义了一个testLocal的方法用来测试Local接口(为什么要这么做,不明白的同学先看看Local的基本知识)
自定义买卖过程中出现的Exceptioin:ProcessingErrorException
封装买卖的结果PO:TradeResult
模拟客户端的买卖行为:Client
配置ejb-jar.xml和weblogic-ejb-jar.xml
1.Remote 接口 Trader.java
import java.rmi.RemoteException;
import javax.ejb.EJBObject;
public interface Trader extends EJBObject {
public abstract TradeResult buy(String customerName, String stockSymbol,
int shares) throws ProcessingErrorException, RemoteException;
public abstract TradeResult sell(String customerName, String stockSymbol,
int shares) throws ProcessingErrorException, RemoteException;
public abstract double getBalance() throws RemoteException;
public abstract double getStockPrice(String stockSymbol)
throws ProcessingErrorException, RemoteException;
public abstract double testLocal() throws RemoteException;
}
2.Home 接口 TraderHome.java
import java.rmi.RemoteException;
import javax.ejb.CreateException;
import javax.ejb.EJBHome;
import javax.ejb.EJBObject;
public interface TraderHome extends EJBHome {
public Trader create() throws RemoteException,CreateException;
}
3.Local 接口 TraderLocal.java
import javax.ejb.EJBLocalObject;
public interface TraderLocal extends EJBLocalObject{
public abstract TradeResult buy(String customerName, String stockSymbol,
int shares) throws ProcessingErrorException;
public abstract TradeResult sell(String customerName, String stockSymbol,
int shares) throws ProcessingErrorException;
public abstract double getBalance() ;
public abstract double getStockPrice(String stockSymbol)
throws ProcessingErrorException;
public abstract double testLocal();
}
4.LocalHome 接口 TraderLocalHome.java
import javax.ejb.CreateException;
import javax.ejb.EJBLocalHome;
public interface TraderLocalHome extends EJBLocalHome {
public TraderLocal create() throws CreateException;
}
5.Stateful Session Bean TraderBean.java
import javax.ejb.CreateException;
import javax.ejb.RemoveException;
import javax.ejb.SessionBean;
import javax.ejb.SessionContext;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
public class TraderBean implements SessionBean {
static final boolean VERBOSE = true;
private SessionContext ctx;
private Context environment;
private double tradingBalance;
public void setSessionContext(SessionContext ctx) {
log("setSessionContext called");
this.ctx = ctx;
}
public void ejbActivate() {
log("ejbActivate called");
}
public void ejbPassivate() {
log("ejbPassivate called");
}
public void ejbRemove() {
log("ejbRemove called");
}
public void ejbCreate() throws CreateException {
log("ejbCreate called");
try {
InitialContext ic = new InitialContext();
environment = (Context) ic.lookup("java:comp/env");
} catch (NamingException ne) {
throw new CreateException("Could not look up context");
}
this.tradingBalance = 0.0;
}
public TradeResult buy(String customerName, String stockSymbol, int shares)
throws ProcessingErrorException {
log("buy (" + customerName + ", " + stockSymbol + ", " + shares + ")");
double price = getStockPrice(stockSymbol);
tradingBalance -= (shares * price); // subtract purchases from cash
// account
return new TradeResult(shares, price, TradeResult.BUY);
}
public TradeResult sell(String customerName, String stockSymbol, int shares)
throws ProcessingErrorException {
log("sell (" + customerName + ", " + stockSymbol + ", " + shares + ")");
double price = getStockPrice(stockSymbol);
tradingBalance += (shares * price);
return new TradeResult(shares, price, TradeResult.SELL);
}
public double getBalance() {
return tradingBalance;
}
public double getStockPrice(String stockSymbol)
throws ProcessingErrorException {
try {
return ((Double) environment.lookup(stockSymbol)).doubleValue();
} catch (NamingException ne) {
throw new ProcessingErrorException("Stock symbol " + stockSymbol
+ " does not exist");
} catch (NumberFormatException nfe) {
throw new ProcessingErrorException("Invalid price for stock "
+ stockSymbol);
}
}
public double testLocal(){
Double balance=1.00;
try{
InitialContext ic = new InitialContext();
TraderLocalHome localHome=(TraderLocalHome)ic.lookup("ejb/TraderEJB");
TraderLocal localTrader = (TraderLocal) localHome.create();
balance=localTrader.getBalance();
localTrader.remove();
}catch(Exception e){
log("local exception");
}
return balance;
}
private void log(String s) {
if (VERBOSE) {
System.out.println(s);
}
}
}
6.自定义Exception:ProcessingErrorException
public class ProcessingErrorException extends Exception {
public ProcessingErrorException() {}
public ProcessingErrorException(String message) {super(message);}
}
7.Trade买卖结果封装的POJO:TradeResult
import java.io.Serializable;
public final class TradeResult implements Serializable {
public static final int SELL = 0;
public static final int BUY = 1;
private int numberTraded; // Number of shares really bought or sold
private int action; // Whether shares were bought or sold
private double price; // Price shares were bought or sold at
public TradeResult(int numberTraded, double price, int action) {
this.numberTraded = numberTraded;
this.price = price;
this.action = action;
}
public int getNumberTraded() {
return numberTraded;
}
public int getActionTaken() {
return action;
}
public double getPrice() {
return price;
}
public String toString() {
String result = numberTraded + " shares";
if(action == SELL) {
result += "sold";
} else {
result += "bought";
}
result += " at a price of " + price;
return result;
}
}
8.客户端调用EJB的程序:Client.java
import java.rmi.RemoteException;
import java.util.Hashtable;
import javax.ejb.CreateException;
import javax.ejb.RemoveException;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.rmi.PortableRemoteObject;
public class Client {
private static final String JNDI_NAME = "ejb20-statefulSession-TraderHome";
private String url;
private TraderHome home;
public Client(String url) {
this.url = url;
}
public static void main(String[] args) throws Exception {
log("\nBeginning statefulSession.Client...\n");
String url = "t3://localhost:7001";
Client client = null;
// Parse the argument list
if (args.length > 1) {
log("Usage: java examples.ejb.ejb20.basic.statefulSession.Client t3://hostname:port");
return;
} else if (args.length == 1) {
url = args[0];
}
try {
client = new Client(url);
client.example();// remote
} catch (NamingException ne) {
log("Unable to look up the beans home: " + ne.getMessage());
throw ne;
} catch (Exception e) {
log("There was an exception while creating and using the Trader.");
log("This indicates that there was a problem communicating with the server: "
+ e);
throw e;
}
log("\nEnd statefulSession.Client...\n");
}
public void example() throws CreateException, ProcessingErrorException,
RemoteException, RemoveException, NamingException {
String customerName = "Matt";
// Create a Trader
log("Creating trader\n");
home = lookupHome();
Trader trader = (Trader) narrow(home.create(), Trader.class);
// Sell some stock
String stockName = "MSFT";
int numberOfShares = 200;
log("Selling " + numberOfShares + " of " + stockName);
TradeResult tr = trader.sell(customerName, stockName, numberOfShares);
log(tr.toString());
// Buy some stock
stockName = "BEAS";
numberOfShares = 250;
log("Buying " + numberOfShares + " of " + stockName);
tr = trader.buy(customerName, stockName, numberOfShares);
log(tr.toString());
// Get change in Cash Account from EJBean
log("Change in Cash Account: $" + trader.getBalance() + "\n");
log("Local Ejb test start...");
log("testing localTrader balance is:" + trader.testLocal());
log("Local Ejb test end...");
log("Removing trader\n");
trader.remove();
}
/**
* RMI/IIOP clients should use this narrow function
*/
private Object narrow(Object ref, Class c) {
return PortableRemoteObject.narrow(ref, c);
}
/**
* Lookup the EJBs home in the JNDI tree
*/
private TraderHome lookupHome() throws NamingException {
// Lookup the beans home using JNDI
Context ctx = getInitialContext();
try {
Object home = ctx.lookup(JNDI_NAME);
return (TraderHome) narrow(home, TraderHome.class);
} catch (NamingException ne) {
log("The client was unable to lookup the EJBHome. Please make sure ");
log("that you have deployed the ejb with the JNDI name "
+ JNDI_NAME + " on the WebLogic server at " + url);
throw ne;
}
}
/**
* Using a Properties object will work on JDK 1.1.x and Java2 clients
*/
private Context getInitialContext() throws NamingException {
try {
// Get an InitialContext
Hashtable<String, String> h = new Hashtable<String, String>();
h.put(Context.INITIAL_CONTEXT_FACTORY,
"weblogic.jndi.WLInitialContextFactory");
h.put(Context.PROVIDER_URL, url);
return new InitialContext(h);
} catch (NamingException ne) {
log("We were unable to get a connection to the WebLogic server at "
+ url);
log("Please make sure that the server is running.");
throw ne;
}
}
private static void log(String s) {
System.out.println(s);
}
}
9.ejb-jar.xml
<ejb-jar> <enterprise-beans> <session> <ejb-name>TraderEJB</ejb-name> <home>ejb.stateful.TraderHome</home> <remote>ejb.stateful.Trader</remote> <local-home>ejb.stateful.TraderLocalHome</local-home> <local>ejb.stateful.TraderLocal</local> <ejb-class>ejb.stateful.TraderBean</ejb-class> <session-type>Stateful</session-type> <transaction-type>Container</transaction-type> <env-entry> <env-entry-name>BEAS</env-entry-name> <env-entry-type>java.lang.Double</env-entry-type> <env-entry-value>100.00</env-entry-value> </env-entry> <env-entry> <env-entry-name>MSFT</env-entry-name> <env-entry-type>java.lang.Double</env-entry-type> <env-entry-value>150.00</env-entry-value> </env-entry> </session> </enterprise-beans> <assembly-descriptor> <container-transaction> <method> <ejb-name>TraderEJB</ejb-name> <method-name>*</method-name> </method> <trans-attribute>Required</trans-attribute> </container-transaction> </assembly-descriptor> </ejb-jar>
10.weblogic-ejb-jar.xml
<weblogic-ejb-jar>
<weblogic-enterprise-bean>
<ejb-name>TraderEJB</ejb-name>
<stateful-session-descriptor/>
<jndi-name>ejb20-statefulSession-TraderHome</jndi-name>
<local-jndi-name>ejb/TraderEJB</local-jndi-name>
</weblogic-enterprise-bean>
</weblogic-ejb-jar>
11.run Client.java测试结果
Beginning statefulSession.Client...
Creating trader
Selling 200 of MSFT
200 sharessold at a price of 150.0
Buying 250 of BEAS
250 sharesbought at a price of 100.0
Change in Cash Account: $5000.0
Local Ejb test start...
testing localTrader balance is:0.0
Local Ejb test end...
Removing trader
End statefulSession.Client...