Multiple selector

Exercise

Given the following input payload:

<?xml version="1.0"?>
<catalog>
   <book id="bk101">
      <author>Gambardella, Matthew</author>
      <title>XML Developer's Guide</title>
      <genre>Computer</genre>
      <price>44.95</price>
      <publish_date>2000-10-01</publish_date>
      <description>An in-depth look at creating applications
      with XML.</description>
   </book>
   <book id="bk102">
      <author>Ralls, Kim</author>
      <title>Midnight Rain</title>
      <genre>Fantasy</genre>
      <price>5.95</price>
      <publish_date>2000-12-16</publish_date>
      <description>A former architect battles corporate zombies,
      an evil sorceress, and her own childhood to become queen
      of the world.</description>
   </book>
   <book id="bk103">
      <author>Corets, Eva</author>
      <title>Maeve Ascendant</title>
      <genre>Fantasy</genre>
      <price>5.95</price>
      <publish_date>2000-11-17</publish_date>
      <description>After the collapse of a nanotechnology
      society in England, the young survivors lay the
      foundation for a new society.</description>
   </book>
</catalog>

Write a DataWeave transformation that produces the following JSON output:

{
  "authors": [
    "Gambardella, Matthew",
    "Ralls, Kim",
    "Corets, Eva"
  ]
}

Hints

• With xml, where tags tend to repeat, we can use the multiple selector .* to get those repeated tags at the same level.
• The multiple selector will always return an Array.

---

🔒🔓Show solution

%dw 2.0
output application/json
---
{
    authors: payload.catalog.*book.author
}

Notes:

1. Since book is a tag that repeats several times, we can use payload.catalog.*book to get every book. If we used just payload.catalog.book we would get the first book only.
2. Since payload.catalog.*book returns an Array of objects, we can simply append .author, which returns every value whose key is Author, building the new Array we are after.