unXml

Java 8 or later Library for mapping XPaths to JSON-attributes. It parses org.w3c.dom XML Nodes and creates Jackson JsonNodes.

Latest release

The most recent release is unXml 0.9, released November 16, 2017.

To add a dependency on unXml using Maven, use the following:

<dependency>
  <groupId>com.nerdforge</groupId>
  <artifactId>unxml</artifactId>
  <version>0.9</version>
</dependency>

Parser

A Parser	Created by	has apply(node) that does the transformation
Parser<ObjectNode>	parsing.obj().build()	Node ➝ ObjectNode
Parser<ArrayNode>	parsing.arr(...).build()	Node ➝ ArrayNode

Document can also be used as input, since it extends Node.

Using Parsing to create a Parser

To create a Parser you first need an instance of Parsing.

Parsing parsing = ParsingFactory.getInstance().create();

// create parser that will output a Jackson ObjectNode
Parser<ObjectNode> parser = parsing.obj()
  .attribute("resultKey", "//my-xpath")
  .build();
  
Parser<ObjectNode> parser2 = parsing.obj("//my-root")
  .attribute("id", "@id")
  .build();

// create parser that will output a Jackson ArrayNode
Parser<ArrayNode> parser3 = parsing.arr("//my-root)
  .attribute("id", "@id")
  .build();

Parsing to an Object or List

By using the as-method on ObjectNodeParserBuilder or ArrayNodeParserBuilder, you can have Jackson instansiate an Object or a List as part of the parsing process.

// create a parser that will output an Object instance
ObjectParser<Foo> fooParser = parsing.obj(...).attribute(...).as(Foo.class);
Foo foo = fooParser.apply(xmlDocument);

// create a parser that will output a List of objects
ObjectParser<List<Bar>> barsParser = parsing.arr(...).as(Bar.class);
List<Bar> bars = barsParser.apply(xmlDocument);

Example - Parsing an object

The input XML string

<root>
  <id>1</id>
  <title>mytitle</title>
</root>

Creating the Parser

import com.nerdforge.unxml.Parsing;
import com.nerdforge.unxml.factory.ParsingFactory;
...

public class MyController {
  public ObjectNode getJsonFromXml(String inputXmlString) {
    Parsing parsing = ParsingFactory.getInstance().create(); // (1)
    Document document = parsing.xml().document(inputXmlString); // (2)
    
    Parser<ObjectNode> parser = parsing.obj("root") // (3)
      .attribute("id", "id", parsing.number()) // (4)
      .attribute("title") // (5)
      .build(); // (6)

    ObjectNode node = parser.apply(document); // (7)
    return node;
  }
}

1. Uses the ParsingFactory to get an instance of Parsing.
2. Parsing also gives access to an XML-utility object by using the xml()-method.
3. The Parsers.obj() returns an ObjectNodeParserBuilder
4. The resulting json object gets attribute with key = id.

• The value is first read as the String content of the xpath: /root/id in the xml.
• It will apply the SimpleParser.numberParser() method, to the Stringcontent, and return the attribute as a JS Number.

5. The resulting json object gets an attribute with id = title, and from the content on the xpath title.
6. Creates a Parser that will output an ObjectNode.
7. Node ➝ ObjectNode

Return Json object

{
  "id":1,
  "title":"mytitle"
}

Example - Parsing arrays

The input XML string

<root>
  <entry>
  </entry>
  <entry>
    <list>
      <value>x</value>
      <value>y</value>
    </list>
  </entry>
</root>

Creating the Parser

public class MyController {
  @Inject private Parsing parsing; // (1)

  public ArrayNode getArrayFromXml(String inputXmlString) {
    Document document = parsing.xml().document(inputXmlString);
    
    Parser<ArrayNode> parser = parsing.arr("/root/entry",
      parsing.arr("list/value", parsing.text())
    ).build(); // (2)

    ArrayNode node = parser.apply(document);
    return node;
  }
}

1. By using Google Guice you can directly inject a Parsing object into your class. (Remember to install the UnXmlModule in your module).
2. Creates a Parser<ArrayNode>, that can map to an ArrayNode of ArrayNode of Strings.

• The first arr() will pick out each entry node (in the xml-file).
• The second arr() will pick out each value in the list.

Return Json object

[[],["x","y"]]

Example - Complex structures

You can of course combine Parser with Parser and predefined parsers to map to more complex structures.

The input XML string

<?xml version="1.0"?>
<feed xmlns="http://www.w3.org/2005/Atom">
  <entry id="1">
    <name>Homer Simpson</name>
    <birthday>1956-03-01</birthday>
    <email xmlns="http://www.w3.org/2007/app">chunkylover53@aol.com</email>
    <phoneNumbers>
      <home>5551234</home>
      <mobile>5555678</mobile>
      <work>5559991</work>
    </phoneNumbers>
  </entry>
</feed>

Creating the Parser

public class MyController {
  public ArrayNode getUsersFromXml(String inputXmlString) {
    Parsing parsing = ParsingFactory.getInstance(namespaces()).create(); // (1)
    Document input = parsing.xml().document(inputXmlString);
    Parser dateParser = parsing.simple().dateParser(DateTimeFormatter.ofPattern("yyyy-MM-dd")); // (2)

    Parser<ArrayNode> parser = parsing.arr("/a:feed/a:entry", // (3)
      parsing.obj()
        .attribute("id", "@id", parsing.number()) // (4)
        .attribute("name", "a:name")
        .attribute("birthday", "a:birthday", dateParser)
        .attribute("email", "app:email") // (5)
        .attribute("phoneNumbers", parsing.arr("a:phoneNumbers/*", parsing.with(Integer::parseInt))) // (6)
    ).build();
    ArrayNode node = parser.apply(input);
    return node;
  }
  
  private Map<String, String> namespaces(){
    return new HashMap<String, String>(){{
        put("a", "http://www.w3.org/2005/Atom");
        put("app", "http://www.w3.org/2007/app");
    }};
  }
}

1. Creates the instance of Parsing, but with XML-namespaces.
2. Creates a dateParser that will parse dates with the format yyyy-MM-dd.
3. Uses the preconfigured namespace a to do selections.
4. The xpath selects on an attribute in the xml
5. Use the preconfigured namespace app to select the email.
6. We do a xpath selection on a wildcard, to create an array. The String contents of the nodes are parsed into Integers.

Return Json object

[{
  "birthday":[1956,3,1], // (1)
  "name":"Homer Simpson",
  "id":1,
  "email":"chunkylover53@aol.com",
  "phoneNumbers":[5551234,5555678,5559991]
}]

1. The Jackson library will map a Java LocalDate as a JavaScript Array of Numbers. See the documentation.

Functional interface

Since a Parser is a functional interface, it can be mapped directly, like this:

Parsing parsing = ParsingFactory.getInstance(namespaces).create();
Parser<ObjectNode> parser = parsing.obj()... // se above for examples
Document document = parsing.xml().document(inputXmlString);

// Apply to an Optional
Optional<ObjectNode> result = Optional.of(document).map(parser); // (1)

// Apply to a Stream
List<Document> documents = ...
List<ObjectNode> results = documents.stream().map(parser).collect(toList()); // (2)

1. Applies the parser directly without doing a Optional.of(document).map(parser::apply)
2. Shorthand for documents.stream().map(parser::apply).collect(toList())