JSP :: What Is The Use Of Page Implicit Object
Aug 21, 2014
I know that there are 9 implicit objects that are available in a JSP page , except the page implicit object every object has certain utility ,but i am not able to understand the usage of a 'page' implicit object.
I've read it is actually an object of the servlet which is obtained after compiling this JSP page ,moreover a reference of Object class hold this 'page' object so there are only those 11 legacy methods of Object class which anyone can invoke on it and even if the 'page' object is typecasted to our generated servlet class it will also be of no use until there are any instance methods or fields(which are not Thread-safe) declared through <jsp:declaration> tag ,and writing instance method through jsp:declaration will again bring us to the old discussion of avoiding java code from JSPs..
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Aug 21, 2014
The following code snippet will print 'true'.
short s = Short.MAX_VALUE;
char c = s;
System.out.println( c == Short.MAX_VALUE);
Correct Option is : B
A. True
B. False
Explanation:
This will not compile because a short VARIABLE can NEVER be assigned to a char without explicit casting. A short CONSTANT can be assigned to a char only if the value fits into a char.
short s = 1; byte b = s; => this will also not compile because although value is small enough to be held by a byte but the Right Hand Side i.e. s is a variable and not a constant. final short s = 1; byte b = s; => This is fine because s is a constant and the value fits into a byte. final short s = 200; byte b = s; => This is invalid because although s is a constant but the value does not fit into a byte. Implicit narrowing occurs only for byte, char, short, and int. Remember that it does not
occur for long, float, or double. So, this will not compile: int i = 129L;The below code compiles fine and contradicts what is said in bold. So what does the bold statement mean then?
Java Code: class BreakTest{
public static void main(String args[])
{
float f=1.0f;
double d=f;
}
} mh_sh_highlight_all('java');
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May 12, 2015
I need to pass advanced object into controller from JSP page, but I always get null result.It's a controller method:
Java Code:
@RequestMapping(value="admin-user-edit", method=RequestMethod.POST)
public ModelAndView editUser(@ModelAttribute(value="user") UsersEntity user)
{
if (null == user)System.out.println("User is null");
else
System.out.println("User name = " + user.getName() + " | Users id = " + user.getId());
ModelAndView view = new ModelAndView();
return view;
} mh_sh_highlight_all('java');
And this is a JSP page snippet. I need to choose some user from user list and pass it to controller.
XML Code:
<c:forEach var="user" items="${user_list}">
<tr>
<td><c:out value="${user.id}" /></td>
<td><c:out value="${user.name}" /></td>
<td><c:out value="${user.login}" /></td>
<td><c:out value="${user.status}" /></td>
[code]...
I tried to pass it through HttpServletRequest argument but all the same.
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Jan 31, 2015
I have to implement a system where I have to do almost same processing on a jsp page. The slight differences on the present page is based on whether the current page came from page 1 or page 2. So how can I do this?
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Jan 15, 2014
I have a xhtml file that initialization it with ui:repeat tag in realtime.all tags of this page placed under ui:fragment tag.
<edges>
<ui:repeat value="#{graphInfoBean.edges}" var="edge" varStatus="indexVar">
<edge id="#{indexVar.index}" source="#{edge.source}" target="#{edge.target}"
weight="#{edge.weight}">
[Code] ....
When i access to this page and save it as xml in realtime, the tags in xml file saved is empty while it is initialized and everything is working properly.
<edges>
</edges>
How can i access to content of this xhtml page and save it on disk?
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Apr 1, 2015
I have two jsp page one is demo1.jsp and other is demo2.jsp on a click of a particular link on demo1.jsp I want to opwn demo2.jsp inside demo1.jsp without changing layout of demo1.jsp..I tried to use <jsp;include but that doesn't work for me.But how to do this simply on a single link click on a big page?
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Mar 28, 2014
Create an equals method that takes an object reference and returns true if the given object equals this object.
Hint: You'll need 'instanceof' and cast to a (Geocache)
So far I have:
public boolean equals(Object O){
if(O instanceof Geocache){
Geocache j=(Geocache) O;
if (this.equals(j)) //I know this is wrong... but I can't figure it out
return true;
}
else return false;
}
I think I have it correct up to the casting but I don't understand what I'm suppose to do with the this.equals(). Also I'm getting an error that I'm not returning a boolean... I get this all the time in other problems. I don't get why since I have to instances of returning booleans in this. "returns true if the given object equals this object" makes no sense to me. I assume the given object, in my case, is 'O'. What is 'this' object referring to?
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Oct 7, 2014
I am new to Java and have read books, the Java docs, and searched the Internet for my problem to no avail. I have an Array of objects that contains strings. How can I get the object's strings to print in a list so that the user can select that object to manipulate its attributes? For example, the user can select "Guitar 1" from a list and manipulate its attributes like tuning it, playing it, etc. I have a class called Instruments and created 10 guitar objects.Here is the code:
Instrument [] guitar = new Instrument[10];
for (int i = 0; i < 10; i++) {
guitar[0] = new Instrument("Guitar 1");
guitar[1] = new Instrument("Guitar 2");
guitar[2] = new Instrument("Guitar 3");
guitar[3] = new Instrument("Guitar 4");
guitar[4] = new Instrument("Guitar 5");
guitar[5] = new Instrument("Guitar 6");
[code]...
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Mar 27, 2015
can a keyevent in java make the space ship and the laser too ?
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Apr 15, 2014
For example I create an object like this:
BankAccount b = new SavingsAccount();
Now lets say that I want to access a method 'addInterest()' that is in the 'SavingsAccount' class I would have to do: '((SavingsAccount)s).addInterest();'
The question I have is why do I have to cast 'b' to SavingsAccount? Isn't the actual object reference of 'b' already an instance of 'SavingsAccount' class? How does the 'BankAccount' affect the object itself? I'm really confused as to what class is truly getting instantiated and how BankAccount and SavingsAccount are both functioning to make the object 'b'.
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Nov 6, 2014
I don't understand why the object reference variable 'a' cannot be recast from a thisA object reference to a thisB object reference.Is it the case that once a reference variable is linked to a particular object type then it cannot switch object types later on.I am facing the Java Associate Developer exam soon and I am just clearing up some issues in my head around object reference variable assignment,
class thisA {}
class thisB extends thisA { String testString = "test";}
public class CastQuestion2 {
public static void main(String[] args) {
thisA a = new thisA();
thisB b = new thisB();
[code]....
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Nov 19, 2014
I am trying to get this to where I can type in a name and it will search through each object and print back the corresponding object info.
Java Code:
import java.util.Scanner;
public class MyPeople {
public static void main(String[] args) {
Person[] p = new Person[] {
new Person("Chris", 26, "Male", "NJ", "Single"),
new Person("JoAnna", 23, "Female", "NJ", "Single"),
new Person("Dana", 24, "Female", "NJ", "Single"),
new Person("Dan", 25, "Male", "NJ", "Single"),
new Person("Mike", 31, "Male", "NJ", "Married") };
[code]....
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Apr 9, 2014
Task:The main method of the class Things below creates an object called printer deriving from the class PrintingClass and uses that object to print text. Your task is to write the PrintingClass class.
Program to complete:
import java.util.Scanner;
public class Things {
public static void main(String args[]) {
String characterString;
Scanner reader = new Scanner(System.in);
PrintingClass printer = new PrintingClass();
System.out.print("Type in the character string for printing: ");
characterString = reader.nextLine();
printer.Print(characterString);
}
}
// Write the missing class here
Note: In this exercise the solution is part of a conversion unit where many classes have been declared. Because of this the classes are not declared as public using the public attribute.
Example output
Type in the character string for printing: John Doe
John Doe
My Class:
class PrintingClass {
public void print(){
System.out.println(characterString);
}
}
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Mar 23, 2015
If I set a Jlist to contain an array of objects, how can I display properties of each object instead of the object array list itself. Ex:
Instead of:
Person1
Person2
Person3
display values such as each person name within the Jlist:
Mike
Paul
Andrew
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Nov 19, 2014
I have just started working with linked lists. I have a linked list of Objects and I want to be able to search for a specific object. But currently my code continues to return false. Also how would I go about removing the first index of the linked list.
public static void main(String[] args) {
LinkedList<Cookies> ml = new LinkedList<>();
int choice = 0;
while (choice >= 0) {
choice = menu();
[Code] ....
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Dec 27, 2014
I am reading Head First: Java and got to Object References. In the book I got a little bit confused on what happens when two object reference's point at the same object so I wrote a small crude test, the below code. This of course clarified what happens but what I am interested in knowing is in what circumstances would you want to have two separate references for the same object when you could just use the original? Eg. v1
class ObjectValue{
int objVal = 1;
}
class ObjectValueTestDrive{
public static void main(String [] args){
// "Value of v# should be" refers to if it copied the given object values, instead of referencing the same object
ObjectValue v1 = new ObjectValue();
System.out.println("Value of v1 should be 1:" + " "+ v1.objVal);
[code]....
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Aug 18, 2014
Explain anonymous objects with example clearly...i read some where anonymous objects advantage is saving memory...it is benificiable when there is only one time object usage in our program..i can't understand one time usage of object ....i know anonymous objects but i don't know in which context we use them in our programs...i did the anonymous object program with my own example but i can't differentiate this one with normal object..i'm providing my own example below
//anonymous object
public class anonymous {
int x=10;
int y=25;
void display()
{
System.out.println("anomymous");
[code]....
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Jan 15, 2015
What I want to do is have a label that is updated whenever an object gets some new, relevant data.The way you do it in Java looks different from the way we do it in Objective-C. In Objective-C, we have what's known as a protocol. An Objective-C protocol is almost exactly like a Java "implementation." In Obj-C, if I want the user to see the address of where he is, I can have an object that gets the information and invokes a view controller's method; at that point, the view controller would then take the data passed to it and display the data in a label. However, the view controller is an instance of a subclass of the bundled view controller class.
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Jun 11, 2014
I am trying to find either some references to point me on the right track with passing an object with all of it's properties still in tact after it's been created. Currently I am trying to do this through an interface but it seems to just create a new object everytime without the properties. Example below :
import java.util.ArrayList;
import java.util.List;
public interface TPerson{
//public Person p = null;
}
class Thrower {
Person p;
[code]....
When I implement the interface on the other objects as soon as I call the setP method shown above it seems to just create a new one even though I pass the object to the method I want to use.
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Dec 1, 2014
difference between object reference and object
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Oct 26, 2014
I've been trying to learn Java for the last 36 hours or so (after applying for a HTML/CSS job saying "Java knowledge preferred"), and decided to experiment a bit making a graphical tic-tac-toe game. I eventually managed to get that done and it's working. Working code below:
[Java] tic tac toe 1 - Pastebin
So, it works to an extent, however, the way I am capturing which cell is selected seems very sloppy, and would not work if the cells weren't squares or rectangles. So I made a copy of the project and restructured it adding the mouse event to the cells, but now I can't get JComponent to repaint. New code below:
tic tac toe 2 - Pastebin
Curiously, clicking triggers the action for all 9 cells, but I presume it's because I haven't bounded them making it think I've clicked all 9 simultaneously.
What I've tried:
Make the Cell class extend the game class and call this.repaint()- causes stack overflow.
Calling Game.GameState() within the cell clicking event and making that function static - compiler doesn't like calling repaint() inside a static function.
Making another class to make a clone of the Game object and then refresh- was never going to work....
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Sep 22, 2014
I have a value object class and it has the below member
XMLDocument request = null;
Should I instantiate it in the VO class as
XMLDocument request = new XMLDocument();
or leave it null and let the calling program instantiate it?
What's the proper way to do it for Value Object classes in java ?
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Jul 13, 2014
I have this arraylist off a custom object that looks like this witch also contains a list off custom objects
package holders;
import java.util.ArrayList;
public class ManufacturingJobHolder {
private String name;
[code]....
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May 20, 2014
I am trying to use iText to create a PDF document. I found a nice tutorial online but one thing stumps me. How do I get the URL of the JSP page that contains the content? Since this will not be static, I don't want to hard code this. I am sure this is something simple but I am fairly new to servlets and JSP.
String File_To_Convert = "test.htm";
How do I get the url of the JSP page?
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Feb 27, 2015
I have 3 issues -
1-I'd to be able to refresh my page. currently I've set it so it doesn't refresh so I can draw but I want to introduce timed refreshment for example after 30 seconds of drawing the page goes blank and starts again.
2- I'd like to introduce a maximum amount you can draw per each refreshment. E.g the page reloads every 30 seconds and each 30 seconds you have 100 ellipses you can draw, when it refreshes you have a new 100 ellipses
My code below...
PImage bg;
int cNum = 1;
void setup() {
// Images must be in the "data" directory to load correctly
size(1200, 800);
bg = loadImage("User_T_1.jpg");
[code]...
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May 24, 2014
i have jsp file and inside i have list that i get from my servlet . i want to create in the bottom of the page the option to move from one page to another like this " page: 1,2,3,4,5"i try to use the tag <a href=.. and onclick() event ,and i understand that javascript will not work , how can i create the " page: 1,2,3,4,5" ?
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