Use partial wildcards in XPath when reading XML

This example will show you how you can use partial wildcards when reading XML files using XmlReader. Wildcards allow you to match elements dynamically, making it easier to extract data when element names follow a pattern but are not identical.

Input XML file

<?xml version="1.0" encoding="ISO-8859-1"?>
<products>
    <product>
        <id>1</id>
        <name>Laptop</name>
        <Price_Usd>1200</Price_Usd>
        <currency>USD</currency>
    </product>
    <product>
        <id>2</id>
        <name>Smartphone</name>
        <Price_Eur>900</Price_Eur>
        <currency>EUR</currency>
    </product>
    <product>
        <id>3</id>
        <name>Tablet</name>
        <Price_Gbp>750</Price_Gbp>
        <currency>GBP</currency>
    </product>
    <product>
        <id>4</id>
        <name>Headphones</name>
        <Price_Jpy>5000</Price_Jpy>
        <currency>JPY</currency>
    </product>
</products>

Java code listing

package com.northconcepts.datapipeline.examples.cookbook;

import com.northconcepts.datapipeline.core.DataReader;
import com.northconcepts.datapipeline.core.DataWriter;
import com.northconcepts.datapipeline.core.StreamWriter;
import com.northconcepts.datapipeline.job.Job;
import com.northconcepts.datapipeline.xml.XmlReader;

import java.io.File;

public class ReadAnXmlFileUsingWildcard {

    public static void main(String[] args) {
        DataReader reader = new XmlReader(new File("example/data/input/products.xml"))
                .addRecordBreak("//product")
                .addField("Id", "//product/id")
                .addField("Name", "//product/name")
                .addField("Price", "//product/price_*") // This location path will match all nodes that starts with price_
                .addField("Currency", "//product/currency")
                ;
        DataWriter writer = new StreamWriter(System.out);

        Job.run(reader, writer);
    }
}

Code walkthrough

• First an XmlReader is created corresponding to the input file products.xml.
• The  addRecordBreak("//product") is invoked to return a new record whenever a product element ends.
• The Id, Name, Price, and Currency fields are populated via the XmlReader.addField.
• A wildcard is used in addField("Price", "//product/price_*") to match elements whose name begins with price such as <Price_Usd>, <Price_Eur>, and similar variations. 
• StreamWriter is used to write the data to the console.
• Data is transferred from the reader to the writer via Job.run() method. See how to compile and run data pipeline jobs.

Console Output

-----------------------------------------------
0 - Record (MODIFIED) {
    0:[Id]:STRING=[1]:String
    1:[Name]:STRING=[Laptop]:String
    2:[Price]:STRING=[1200]:String
    3:[Currency]:STRING=[USD]:String
}

-----------------------------------------------
1 - Record (MODIFIED) {
    0:[Id]:STRING=[2]:String
    1:[Name]:STRING=[Smartphone]:String
    2:[Price]:STRING=[900]:String
    3:[Currency]:STRING=[EUR]:String
}

-----------------------------------------------
2 - Record (MODIFIED) {
    0:[Id]:STRING=[3]:String
    1:[Name]:STRING=[Tablet]:String
    2:[Price]:STRING=[750]:String
    3:[Currency]:STRING=[GBP]:String
}

-----------------------------------------------
3 - Record (MODIFIED) {
    0:[Id]:STRING=[4]:String
    1:[Name]:STRING=[Headphones]:String
    2:[Price]:STRING=[5000]:String
    3:[Currency]:STRING=[JPY]:String
}

-----------------------------------------------
4 records