Question 1. What Is Jdom?
JDOM is, pretty truely, a Java representation of an XML report. JDOM provides a way to symbolize that record for easy and green reading, manipulation, and writing. It has a trustworthy API, is a lightweight and fast, and is optimized for the Java programmer. It's an alternative to DOM and SAX, although it integrates nicely with both DOM and SAX.
Question 2. What Is Jdom Not?
JDOM is not a wrapper for the W3C's DOM, or any other version of DOM. JDOM is a Java-based totally "document item version" for XML files. JDOM serves the identical purpose as DOM, but is less difficult to use.
JDOM isn't always an XML parser, like Xerces or Crimson. It is a file item version that uses XML parsers to build documents. JDOM's SAX Builder elegance as an instance makes use of the SAX activities generated by way of an XML parser to build a JDOM tree. The default XML parser utilized by JDOM is the JAXP-decided on parser, but JDOM can use almost any parser.
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Question 3. What Is The Jdom License?
JDOM is to be had below an Apache-style open supply license, with the acknowledgment clause removed. This license is many of the least restrictive license available, enabling developers to apply JDOM in growing new merchandise without requiring them to launch their personal merchandise as open supply. This is the license model used by the Apache Project, which created the Apache server. The license is available at the pinnacle of each source document and in LICENSE.Txt within the root of the distribution.
Question 4. Which Maven Artifact Should I Use?
All JDOM variations are to be had inside the 'jdom' vs 'jdom 2' artifact in the org.Jdom group on Maven. The maven artifacts are a large number with early JDOM 2.X versions acting inside the 'jdom' artifacts, and later 2.X variations inside the 'jdom 2' artifact. Maven does now not permit the fixing of mistakes, so maven users wil just should stay with it as it is.
If your task is one which calls for each JDOM 1.X and a couple of.X, then you may also use the 'jdom-legacy' artifact to drag in version 1.1.Three (or later 1.X model).
Question 5. What Is The Jdom Philosophy?
JDOM has been and will continue to be developed with this philosophy:
JDOM must be truthful for Java programmers.
JDOM should help smooth and efficient record change.
JDOM must hide the complexities of XML wherever viable, at the same time as last actual to the XML specification.
JDOM need to combine with DOM and SAX.
JDOM have to be lightweight and rapid.
JDOM must clear up 80% (or extra) of Java/XML issues with 20% (or much less) of the attempt.
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Question 6. Why Is The Jdom Api Defined In Terms Of Concrete Classes Rather Than Interfaces?
This difficulty has been discussed several instances on the JDOM mailing list, with numerous humans on each aspects. In popular, many people feel that a class-primarily based API is better while sub classing isn't always wished, even as an interface-primarily based API is higher while sub classing is wanted. However, either machine may be used in both case.
Jason Hunter summarizes the arguments towards an interface-based totally API for JDOM:
With interfaces the whole thing turns into a manufacturing unit, factors must be 'imported' into new documents instead of simply introduced, features like long-time period serialization can't be guaranteed, and the listing is going on.
We started with interfaces in reality. During our pre-release assessment to a few peers we obtained the feedback we must try concrete training. We did, and the design changed into much better for it.
Think about java.Io.File as an analogy.
There's a reason we are saying:
File figure = new File (document route);
File infant = new File (parent, "aaa.Txt");
FileSystem fs = FileSystem.GetDefaultFileSystem ();
File parent = fs.GetFile (report path);
File baby = fs.GetFile (figure, "aaa.Txt");
The former is without a doubt less difficult and nicer to cope with.
Another point to hold in mind is that something that can be accomplished with interfaces can be performed with sub classing - the most effective penalty is in all likelihood unused variables in the base class.
For reference, the present day mailing list discussion in this topic started Nov. 30, 2000 with "Interfaces", and continued with "Interface-based JDOM" and "Announce: JDOMPlus". It might assist to review this dialogue before bringing this topic up at the mailing listing.
Question 7. How Does Jdom Work With Dom And Sax?
JDOM documents may be constructed from XML documents, DOM bushes, SAX occasions, or some other source. JDOM files can be transformed to XML files, DOM timber, SAX activities, or some other vacation spot. This capability proves beneficial, for instance, whilst integrating with a software that expects SAX events. JDOM can parse an XML document, allow the programmer without difficulty and effectively manage the document, then fire SAX events to the second one software at once - no conversion to a serialized format is necessary.
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Question eight. Was Jdom Designed For Generics?
JDOM was designed earlier than Generics, however JDOM 2.X has taken the proven design of JDOM 1.X and extended it to use Generics where feasible. Specifically, all Collections-based operations require as it should be typed inputs, and go back correctly typed effects. Further, JDOM 2.X takes advantage of different Java five functions like varargs, and co-version go back sorts.
Generics: Element.GetAttributes () returns List<Attribute>, Element.GetChildren () returns List<Element>, and so on.
Co-version Return Types: Element. Clone () returns Element, Text. Detach () returns Text, etc.
I attempted to apply JDOM and get an blunders like this:
Question nine. What's Wrong?
You need to make sure that the xerces.Jar report furnished with the JDOM download is in your classpath before any other XML instructions, including those that come with JAXP or Crimson. These other XML libraries, as well as older versions of Apache Xerces, support DOM Level 1 and SAX 1.Zero, not the required DOM Level 2 and SAX 2.Zero. The end result is an exception being thrown. Check your classpath, and try again. If the classpath seems OK, the difficult JAR can also be hiding inside the system's preferred extension listing.
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Question 10. What Do You Mean "trendy Extension Directory"?
The fashionable extension listing is a listing containing JAR documents this is searched automatically by means of the Java runtime and compiler. If you've established the JDK (now not the just the JRE) you could well have separate ext directories, certainly one of that is used for compiling (generally someplace like C:jdk1.3jrelibext) and the opposite of which is used for walking code (generally someplace like C:Program FilesJava Softjre1.3libext). The incorrect JAR report in both listing can get in your way (even though at specific instances). Furthermore, the right JAR report must be in each directories.
Question eleven. How Do I Avoid The Dom Level 1 Problem In Visual Age For Java?
When the WTE feature is delivered to the workspace, the project 'IBM XML Parser for Java' is delivered as well. This challenge consists of antique DOM Level 1 'org.W3c.*' interfaces. JDOM is based on DOM Level 2, and therefore conflicts with this project.
The solution is to do the subsequent:
Change workspace owner to Administrator
Create open version of the project 'IBM XML Parser for Java'
Delete all the programs that incorporate org.W3c.* interfaces
Version the project.
Create a new Project for DOM Level 2 parser together with Xerces
Import all Xerces instructions consisting of org.W3c.* interfaces (you may use a completely exceptional venture for the ones interfaces if you want to work with other parsers)
Version the Xerces venture
Create a JDOM task and import jdom instructions into it. Version the task.
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Question 12. How Do I Avoid The Dom Level 1 Problem In Websphere?
WebSphere has the identical problem with DOM Level 1 interfaces as VAJ above. The solution is to do one the following:
Put the path to xerces.Jar (or different DOM Level 2 interfaces) inside the variable 'com.Ibm.Ejs.Sm.Adminserver.Classpath' inside the document admon.Config. This is living in $WAS_ROOT$/bin earlier than all different variables.
Or, if you run WAS $WAS_ROOT/bin/debug/adminserver.Bat add a line 'set WAS_CP=xerces.Jar' (or different DOM Level 2 interfaces) before different set WAS_CP commands.
Or, upload JDOM to the software server CLASSPATH, using both the admin.Cfg document or the management console.
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Question 13. What Jdom Version Works With Which Jdk?
JDOM 1.X variations help JDK 1.2 and later.
JDOM 2.X versions help JDK 1.5 and later.
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Question 14. Are There Any Performance Numbers?
The JDOM 2.X improvement procedure protected benchmarks for tracking overall performance adjustments. There are performance numbers evaluating distinctive variations of JDOM 2.X in addition to evaluating the performance of JDOM on exceptional JDK variations.
Dennis Sisonke in the past ran performance benchmarks. In trendy, most XML object models are in a comparable community.
Question 15. How Does Jdom Integrate With Xslt?
There are many ways to do XSL transforms with JDOM. The maximum straightforward way is to apply the usual JAXP Transformer interface and the JDOMSource/JDOMResult training discovered in the org.Jdom2.Remodel package.
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Question 16. Is Jdom Thread Safe?
The middle API is intentionally no longer thread safe. In different words, there are no synchronized blocks within org.Jdom. This choice makes experience due to the fact we count on the primary JDOM use cases to be:
Single thread reads an XML circulate into JDOM and appears at it examine simplest.
Single thread reads an XML circulate into JDOM and modifies it.
Single thread reads an XML circulate into JDOM and makes it to be had to a run time machine for study handiest get entry to.
The use case wherein a "Single thread reads an XML circulation into JDOM and exposes it to a couple of threads to regulate its contents" within reason uncommon. In that case, JDOM can nonetheless be made thread secure but the programmer simply has to carry out their personal synchronization, perhaps as synchronizing on the Document instance.
On the alternative hand, there are certain features that require 'operational' components of JDOM to be thread secure:
org.Jdom2.Namespace.GetNamespace () is safe
All factory-kind training are safe (XPathFactory, etc.)
Question 17. Why Does Equals () Only Do A == Check?
In JDOM two Content items are handiest equal if they're the precise same item. This shall we a call like listing. Remove (elem) take away simplest the precise Element handed in, no longer any element that's equivalent. That's a completely vital distinction. Doing a complete equals() on an Element would require recursing down the tree, and in preferred we trust it not likely you'll want to recognise if this element and all its youngsters are equivalent to another one. If you truely do want to recognise you could write some assessment code your self that exams best as an awful lot as you need to test (maybe the call/namespaces most effective) in place of doing a full recurse.
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Question 18. Why Is Equals () Declared Final?
The equals () techniques are very last for JDOM Content lessons in order that a subclass can't spoil the == behavior this is required for calls like list. Remove (elem) to work as designed. Similarly, the hashCode () strategies are also final (to hold the equals/hashCode agreement).
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Question 19. How Do I Construct A Document From A String?
You use standard Java IO library calls. Wrap the String with a String Reader and pass the reader to SAX Builder:
Document document = builder. Build (new String Reader (xml));
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Question 20. How Do I Remove An Element Or Other Content?
Use the strategies at the List returned through get Children () or get Content (). JDOM does no longer need unique methods due to the fact the methods exist already in List.
For instance to get rid of an element from a listing of kids:
List kids = discern.GetChildren ();
Children. Remove (detail); // given toddler
Children. Remove (0); // first infant
Other methods on List provide alternatives to take away all children, upload a infant at a given area, and so on.
If you have got a specific Element or other Content which you need to get rid of from its discern, you could detach the Content with the Content. Detach () technique.
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Question 21. How Do I Move An Element From One Place To Another?
There's no need for node "importing" like there's with DOM. Just get rid of the element from its modern region, after which add the detail to its new area. The detail's content (together with its element kids) will clearly "tag" alongside for the ride. You have to get rid of the element earlier than including it to its new area because elements can also have most effective one discern lower back by means of get Parent ().
New Parent.Add Content (elt.Detach ());
Question 22. How Do I Copy An Element From One Place To Another?
There's no need for node "uploading" like there is with DOM. Just clone the element being copied and upload its clone in its new region. You have to clone the element earlier than adding it to its new location because elements may additionally have only one parent lower back with the aid of get Parent ().
NewParent.AddContent (elt.Clone ());
Question 23. Can An Element Or Attribute Name Contain A Colon?
The XML 1.Zero specification in particular reserves the colon person to be used with XML Namespaces. No different use is compliant with XML 1.0. Therefore JDOM does now not will let you create detail and attribute names that incorporate colons besides whilst the usage of namespaces. Furthermore, due to the way namespaces are carried out in JDOM, you can't honestly create an Element or Attribute with a totally qualified call like svg: name.
That is you can't do that:
Element e = new Element ("svg: title");
Instead you need to break up the 2 elements into a Namespace and a local call. This is the right JDOM way to create an element in a namespace:
Element e = new Element ("title", "svg", "http://www.W3.Org/2000/svg");
The first argument is the nearby name. The 2nd argument is the prefix. The third argument is the namespace URI.
If you are trying to create the xml: Lang and xml: area attributes use:
Element e = new Element ("lang", Namespace.XML_NAMESPACE);
Question 24. Why Do I Need To Pass In A Namespace To Get Child (), When The Child Element I'm Looking For Has No Namespace Declaration?
Specifically, for this XML fragment:
You want to use code like this:
Namespace ns = Namespace.GetNamespace ("http://foo.Com");
Element y = x.GetChild ("y", ns);
Element z = y.GetChild ("z", ns);
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Question 25. Why Do All New Lines Appear As N, Even On Windows?
According to segment 2.Eleven of the XML Recommendation, 2d version:
To simplify the duties of applications, an XML processor have to normalize line breaks in parsed entities to #xA either with the aid of translating the 2-person sequence #xD #xA and any #xD that is not observed through #xA to #xA on input before parsing, or by the use of some other approach such that the characters passed to the utility are similar to if it did this translation.
In different phrases, that is exactly what's speculated to appear.
Some XML enter may additionally get away the r carriage go back as
and the XML parser will translate this in to a real r character in your JDOM Text. When this Text is output again it will be re-escaped as
Question 26. Why Does Set Text (" ;") Not Do What I Want?
When you skip a string into a technique like set Text () JDOM assumes it is simply that, a string, no longer a fragment of XML. For example, whilst you call:
element.SetText ("&#a hundred and sixty ;")
JDOM assumes you want to set the content material to the string containing the six characters & # 1 6 zero. It does no longer parse it to attempt to understand it as XML first. Thus whilst you output the text the usage of XMLOutputter it's going to clearly break out the unique ampersand character and output & #one hundred sixty. The solution is to pass everyday Unicode characters to the set Text () technique or, if you have textual content records which you need to be interpreted as XML, skip it thru an XML parser earlier than it goes into JDOM. This is what the SAX Builder and DOM Builder lessons do.
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Question 27. When Using An Ide Debugger Why Do I See A Strange Array Index Out Of Bounds Exception?
Some parsers (Xerces consist of) use this exception as part of their wellknown working method, internally throwing and catching the exception. No code outside the library is meant see it. However, IDE debuggers are regularly configured to document any time this exception is thrown, and as a result they divulge the exception. It can be properly ignored.
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Question 28. Why Does My File Encoding On Output Not Match The Encoding On Input?
The default character encoding used by XMLOutputter is UTF-eight, a variable-period encoding which can constitute all Unicode characters. This can be changed with a name to layout.Set Encoding () at the Format item handed to XMLOutputter. It could be pleasant if XMLOutputter could default to the original encoding for a file, however lamentably parsers don't imply the unique encoding. You have to set it programmatically.
This trouble most usually affects human beings with files inside the commonplace ISO-8859-1 (Latin-1) encoding who use characters like ñ but are not familiar with having to think about encodings. The tip to consider is that with these documents you have to set the output encoding to ISO-8859-1, in any other case characters within the variety 128-255 can be output the usage of a double byte encoding in UTF-eight as opposed to the regular unmarried byte encoding of ISO-8859-1.
Question 29. How Can I Perform In-reminiscence Validation Against A Dtd Or Schema?
Currently you can not do this, in JDOM or every other Java report item model API. However, this is something we'd like JDOM to support, and we have a volunteer who is operating on it.
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Question 30. Jdom Ensures The Document In Memory Is Always Well-formed. Can Jdom Also Ensure The Document In Memory Is Always Valid?
No, it's our modern-day notion that it is higher to show a check Valid () sort of name than to strive steady validation checking. One cause is performance. A second purpose is that you have a fowl-and-egg problem where as an instance an element needs exactly toddler factors to be legitimate, but after adding both baby the document could be in a temporarily invalid state. To work around this would require something like transactional modifications, and that is quite a few overhead for little advantage.
Question 31. How Do I Post To The Mailing List From Multiple Addresses?
For junk mail safety, most effective individuals of the mailing list may also submit. To put up from multiple accounts, subscribe every account and set the "Disable mail transport" characteristic to "On" for all the extra accounts.
Question 32. The Book Java And Xml Talks About Jdom 1.0; Why The Confusion?
The book covers an early beta. Much has changed (for the better) when you consider that publication of the e book. For the most accurate JDOM API believe the Javadoc, now not the book. Brett turned into a bit positive whilst writing the e-book. His 2nd Edition units matters immediately.
Question 33. How Do I Submit A Bug Report?
If you agree with you found a worm in JDOM:
Check both the open troubles and closed troubles to see if it is a regarded issue.
Check if the hassle happens when the use of the modern improvement model (supply .Zip) of JDOM.
Search the JDOM mailing list data as defined above.
If you do not locate resolution with the cutting-edge photograph, either create an difficulty on GitHub or publish to the jdom-interest mailing list; make certain you are a subscriber first as best subscribers can put up.
In the computer virus document, give as a whole lot statistics as viable -- the stack strains, a reproducible and quick code example, the XML document inflicting problems. Make sure to country the version of JDOM used (legitimate version or GitHub devote).
If you have a patch to fix the computer virus, please put up that in conjunction with the problem document. We love patches.
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