Adwin Lorance

Hi

Recently I came up with a problem of interacting with a Payment Gateway. The problem I faced was to maintain the session between our site and the merchant site.

Any suggestions on how it can be achieved? The merchant site has given a URL to which I need to post my form. They have also asked for a landing page(in our site) where they will send the response after making the payment. As soon as I post my request , the session object of my JSP is destroyed; and when they send the response back, a new session object is created.

Any suggestions are welcome to solve this issue.

Ok , let me share what I think ...

There are 2 types of exception
Checked and Unchecked Exception.

Checked Exception : Object of type Exception or its sub class , except the runtime exception.
Unchecked Exception : Object of Type Runtime Exception and its sub type.

Compiler forces you to handle/declare any checked exceptions.

Compiler does not force you to handle/declare any unchecked exceptions , as you cannot predict whether an unchecked exception can occur.

But still , you can handle it.

Error - It is unchecked , as you cannot predict when an Error can occur.
Also , you cannot handle it.

True .. As Ninad says , Container is responsible to create Threads and give each request to a new Thread. Or else pick from a pool of servlet instances and let it handle a request.

What did you want to do in a multi threaded environment ?

Hii

I was trying to consume a Web service exposed in the internet . I made a Webservice Client in Eclipse by giving the wsdl path of the service. But when I am trying to access the service , I am getting the following exception.

[INFO] Unable to sendViaPost to url[http://www.webservicex.net/globalweather.asmx]
java.net.NoRouteToHostException: No route to host: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(Unknown Source)
at java.net.PlainSocketImpl.connectToAddress(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.commons.httpclient.protocol.ReflectionSocketFactory.createSocket(ReflectionSocketFactory.java:140)
at org.apache.commons.httpclient.protocol.DefaultProtocolSocketFactory.createSocket(DefaultProtocolSocketFactory.java:125)
at org.apache.commons.httpclient.HttpConnection.open(HttpConnection.java:707)
at org.apache.commons.httpclient.MultiThreadedHttpConnectionManager$HttpConnectionAdapter.open(MultiThreadedHttpConnectionManager.java:1361)
at org.apache.commons.httpclient.HttpMethodDirector.executeWithRetry(HttpMethodDirector.java:387)
at org.apache.commons.httpclient.HttpMethodDirector.executeMethod(HttpMethodDirector.java:171)
at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:397)
at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:346)
at org.apache.axis2.transport.http.AbstractHTTPSender.executeMethod(AbstractHTTPSender.java:542)
at org.apache.axis2.transport.http.HTTPSender.sendViaPost(HTTPSender.java:189)
at org.apache.axis2.transport.http.HTTPSender.send(HTTPSender.java:75)
at org.apache.axis2.transport.http.CommonsHTTPTransportSender.writeMessageWithCommons(CommonsHTTPTransportSender.java:371)
at org.apache.axis2.transport.http.CommonsHTTPTransportSender.invoke(CommonsHTTPTransportSender.java:209)
at org.apache.axis2.engine.AxisEngine.send(AxisEngine.java:448)
at org.apache.axis2.description.OutInAxisOperationClient.send(OutInAxisOperation.java:401)
at org.apache.axis2.description.OutInAxisOperationClient.executeImpl(OutInAxisOperation.java:228)
at org.apache.axis2.client.OperationClient.execute(OperationClient.java:163)
at net.webservicex.www.GlobalWeatherStub.GetCitiesByCountry(GlobalWeatherStub.java:200)
at net.webservicex.www.WeatherClient.main(WeatherClient.java:28)


Any idea about the problem?

Thanks in advance.

Adwin

Serialization is definitely there in the SCJP 6 exam.

Cheers

------------------------------------------------------------------------------------------------------------------------------------------------
SCJP 6 80%

This belongs to the Model i.e. the POJO that you will write.

Hii .. just wanted to share why a method local inner class can access final variables...

As you must be knowing that when we compile a class having a method local inner class , the compiler makes 2 class files.
e.g. outer.class and outer$inner.class

Now imagine , if you could pass non final variables to a function inside the inner class. How will the JVM pass a variable from one class to a function in another class.
To solve this problem , the JVM makes a requirement that the developer mark the variable as FINAL.

How does it solve the problem?

when you mark a variable as final in the outer class , the compiler places a hidden variable (e.g. val$var ) in the compiled inner class file.
The value of this hidden variable and the final variable declared in the outer class will be same. And as it is final , it cannot change at the runtime. Also , the final variables has to be assigned before the compilation.

So problem solved.
I hope I was clear.

Hi .. you can create a WAR file using the JAR utility available. The only pre requisite is that you need to prepare a proper deployment folder structure and a proper deployment descriptor.

The command is as follows - " jar -cvf MyWarFileName.war".
Execute this command from the command line after going to the appropriate folder.

Whether there is way to only include .class files?

Well , whatever you keep in the folder on which you are running the JAR utility , will be included in the WAR file.

For e.g. The normal folder structure will be like below.

MyApplication | | |----------------------------------------- WEB-INF | | | |---- Classes | |------ JSPs |------ HTMLs
Place the package structure in the classes folder. And the Deployment Descriptor directly under the WEB-INF folder.

Thanks

[BPS: Added to code tags to dir tree to show indents.]

That is correct , Thread implements Runnable .. But it is always a good practice to implement the interface Runnable than extending Thread , as it gives you flexibility to inherit from other classes.. Anyways , it wont make a difference if you extend from Thread or implement Runnable ..

Adwin