Develop Reference

How to create an XML document programmatically in Java?

Given a pre-described set of tags which I can use(for example, a structure like the AndroidManifest.xml), how can I create an XML document (for a manifest file) from scratch in Java, preferably not using any third party libraries?
Also, what is(if any) the best way to do this?

There are many ways to generate XML without third party framework
SAX and DOM (powerful yet complex)
Jax-B (relatively easy)
The simplest way to generate an XML is to use Jax-B (which comes as a standard from JEE6 onwards).Refer here for more details on Jax-B
But if your trying to implement this in Android(since you mentioned AndroidManifest.xml) then I recommend you to use some third party framework like Simple to avoid unwanted complications, because it is more lightweight than the rest of the above mentioned technologies and easy to use.
If your strict on not using third party library(which I do not recommend), then use SaxParser in Android, refer here for some examples.
Hope this helps

Overview of Java DOM API for XMLType
Oracle XML DB supports the Java Document Object Model (DOM) Application Program Interface (API) for XMLType. This is a generic API for client and server, for both XML schema-based and non-schema-based documents. It is implemented using the Java package oracle.xdb.dom. DOM is an in-memory tree-based object representation of XML documents that enables programmatic access to their elements and attributes. The DOM object and interface are part of a W3C recommendation. DOM views the parsed document as a tree of objects.
http://docs.oracle.com/cd/B19306_01/appdev.102/b14259/xdb11jav.htm
http://www.c-sharpcorner.com/UploadFile/yougerthen/how-to-generate-an-xml-document-programmatically-using-system-xml-xmlwriter-part-iii/

How to insert data from xml document to postgresql?

I have a table in PosgreSQL.
I have an xml schema.
I want to create an xml document with this schema and data from Postgre.
What should I read to work with xsd in java? And what are the best tools to use?
UPDATE
More specific question. Can i create data base in PostgreSql using xml schema?
UPDATE 2
Okey. I create data base from .xsd using XMLSpy.
Now i need load xml document in this data base. What i gonna do?
UPDATE 3
Okay. I generate java classes using JiBX.
Now i want to read xml file and write data from this to data base. What i gonna do?

Probably best to generate java classes for the XML from the XSD, you can read about it here:
Generate Java classes from .XSD files...?

I dont know anything about the postgreSql, but i will suggest you to generate java classes from your Xsd using jaxb and use those classes as domain for your db.

yes, the best way to accomplish the above task would be to generate java class and populate your respective beans.
From there on you can insert your values of beans to the respective tables in posgresql

What are the differences between mapping,binding and parsing?

I am starting to learn web-services in java EE6.
I did web development before, but never nothing related to web services.
All is new to me and the books and the tutorials i find in the web are to technical.
I started learning about .xsd schemas and also .xml.
In that topic i feel confident, i understand what are the schemas used for and what validation means.
Now my next step is learning about JAX-B(Java Api for XML Binding). I rode some about it and i did also some practice in my IDE. But i have lots of basic doubts, that make me stuck and cannot feel confident to continue to the next topic.
Ill appreciate a lot if someone could explain me well my doubts:
What does it mean mapping and what is a mapping tool?
What does it mean binding and what is a binding tool?
What does it mean parsing and what is a parsing tool?
How is JAX-B related to mapping,binding and parsing?
I am seeking for a good answer built by you, not just a copy paste from google(Ive already been online a few hours and only got confused).

Based on what I understand..
What does it mean mapping and what is a mapping tool?
In case of Java/XML, mapping is nothing but representing a Java object model
in to an XML document representation ( and vice versa. )
A mapping tool will allow you to convert from one format to another. This is just the definition step.
What does it mean binding and what is a binding tool?
Binding is the process of in-memory(as the application is running) conversion of XML document to object represantation.
Binding is achieved through unmarshalling.
What does it mean parsing and what is a parsing tool?
Parsing is reading an input stream of data and checking whether if the stream of data coforms to certain grammar. Parsing tools consume stream of data and generate errors when the data fails to conforms to grammar that the tool is checking. It would also generate events to indicate that it has received certain "tokens" from the stream. In java/xml scenario, there are multiple types of parsers such as DOM, StAx, SAX...
How is JAX-B related to mapping,binding and parsing?
JAXB mapping:
is when you use xjc to generate java class hierachy based on an XSD
The mapping occurs when classes are generated with JAXB annotations
Mapping tool in the scenario is xjc
JAXB Binding :
Occurs when an application unmarshalls an XML document to Object represanation
(JAXBElement) unmarshaller.unmarshal(
new File("some.xml"));
Parsing :
in order to convert XML document to object represantation, the JAXB engine has to
first "parse" the xml document to ensure correctness and then tokenize to instatiate java objects. This happens internally and you do not control ito ensure correctness and then tokenize to instatiate java objects.

Would strongly suggest that you get a copy of Java Web Services Up and Running and start at chapter 1 and start from there. It is not easy or intuitive, get ready for a long learning curve. Note. All the binding stuff will just confuse you unless you have a basic understanding of how all the pieces work.

Turn off XSD validation of spring files

Spring tries to validate xml confniguration files against xml schemas. Which is fine, but there might be cases when the validation fails (outdated schema, for example). Is there a way to turn off xsd validation?

See this Spring JIRA: https://jira.spring.io/browse/SPR-5014 - has both the team's comments on why they won't directly build it in as well as an example of how to implement yourself.

Declarative XML -> POJO conversion

I have to write a process (in Java) which periodically hits a URL, reads the returned XML document, and persists that data into the DB. This data is further used by my application, so I have modeled them as Hibernate-mapped POJOs.
I can parse the XML and then create appropriate POJOs, but I was looking for a simpler declarative approach. What libraries are available which can take a input configuration and create the POJOs from the XML document?

Another alternative could be JiBX
Also, although you said you don't want to parse the XML, XPath can be a very concise way of extracting the content you are interested in?

JAXB can automatically create classes based on an XML Schema (assuming you have one for the XML source). At runtime, it can then convert the XML document into POJOs representing the XML. It is declarative in that you can tweak the Schema-to-class mapping, a little.
If I understand your task correctly, this is pretty much the use-case JAXB was designed for (though it can do other things too). It's part of Java 1.6 (maybe 1.5 too?), in packages: javax.xml.bind.*

You can use XStream to deserialize the XML and map it directly to the Hibernate-mapped POJOs.
Cheers.

Using Hibernate you can directly map XML to table. This is experimental feature. Check here
http://www.hibernate.org/hib_docs/v3/reference/en-US/html/xml.html

EclipseLink JAXB (MOXy) has extensions for mapping JPA entities to XML (JPA entities have things like embedded ID classes, lazy loading, and compound key relationships that need special handling), I'm not aware of any other OXM solution that does this.
For more information see:
http://wiki.eclipse.org/EclipseLink/Examples/MOXy/JPA