New DocumentMapper for XML and data retrieval using XPath

[oswaldobapvicjr]

New feature

Proposed solution

Introduce a new Mapper -- DocumentMapper -- inside the confectory-core module which allows the mapping of XML sources using standard JDK classes as org.w3c.dom.Document instances and data retrieval using XPath.

Module	Provider(s)	Properties	XML	JSON	YAML
confectory-core	JDK 8+ standard	--	YES	--	--

Examples of usage

Loading a XML file as a Document

Sample file (agents.xml)

<conf>
   <enabled>true</enabled>
   <agents>
      <agent>
         <class>Agent1</class>
         <interval>*/2 * * * *</interval>
      </agent>
      <agent>
         <class>Agent2</class>
         <interval>10s</interval>
      </agent>
   </agents>
</conf>

Code sample (desired):

Configuration<Document> config = Configuration.<Document>builder()
                                .source(new ClasspathFileSource<>("agents.xml"))
                                .mapper(new DocumentMapper())
                                .build();

config.getBean(); // returns an instance of org.w3c.dom.Document
config.getBoolean("//enabled"); // true
config.getString("//agents/agent[1]/class"); // "Agent1"
config.getString("//agents/agent[class='Agent2']/interval"); // "10s"

Task list

The following requirements shall be addressed in this issue:

• New Mapper implementation (suggested name: DocumentMapper) for loading XML sources as org.w3c.dom.Document
• New ConfigurationHelper implementation (suggested name: DocumentConfigurationHelper) to support configuration data retrieval using XPath
• JUnits
• Documentation updates

Quality criteria

The following criteria will be observed during the Code Review:

Code coverage

• Unit tests shall secure the produced code.
• Test unit test coverage shall remain the same or increase (never decrease)

Documentation

• All methods shall be documented with Javadoc, providing examples of usage.
• Javadoc pages shall be compilable with no errors or warnings
• README.md shall be updated if applicable

[codecov]

Codecov Report

Merging #112 (f1f99fa) into master (4f73989) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #112      +/-   ##
============================================
+ Coverage     99.16%   99.20%   +0.03%     
- Complexity      385      408      +23     
============================================
  Files            63       65       +2     
  Lines           721      757      +36     
  Branches         51       53       +2     
============================================
+ Hits            715      751      +36     
  Misses            5        5              
  Partials          1        1              

Impacted Files	Coverage Δ
...nternal/helper/GenericJsonConfigurationHelper.java	100.00% <ø> (ø)
...y/internal/helper/DocumentConfigurationHelper.java	100.00% <100.00%> (ø)
...ava/net/obvj/confectory/mapper/DocumentMapper.java	100.00% <100.00%> (ø)