Java - Untyped data structures

If you use a NoSQL database, it’s common to retrieve documents with an unknown attribute structure. Furthermore, the amount and types of attributes may differ in documents resulting from a single query. Another problem is that you want to add one or more attributes to a document.

There are three solutions to these problems:

• The BaseDocument class
• Jackson JsonNode
• Raw JSON strings

The BaseDocument class

The BaseDocument class can be used to read and write database documents as well as to map AQL bind variables and query results. It implements the following API:

public final class BaseDocument {
    // metadata getters
    public String getId();
    public String getKey();
    public String getRevision();
    // metadata setters
    public void setId(final String id);
    public void setKey(final String key);
    public void setRevision(final String rev);
    // attributes accessors
    public Map<String, Object> getProperties();
    public Object getAttribute(final String key);
    // attributes mutators
    public void setProperties(final Map<String, Object> props);
    public void addAttribute(final String key, final Object value);
    public void updateAttribute(final String key, final Object value);
    public void removeAttribute(final String key);
}

Note: BaseDocument attributes are serialized and deserialized using the driver’s internal serde, which is based on Jackson Databind. Attributes serialization and deserialization cannot be customized.

To create a document from BaseDocument:

BaseDocument doc = new BaseDocument("myKey");
doc.addAttribute("a", "Foo");
doc.addAttribute("b", 42);
collection.insertDocument(doc);

To read a document as BaseDocument:

BaseDocument readDocument = collection.getDocument(key, BaseDocument.class);
System.out.println("Key: " + readDocument.getKey());
System.out.println("Attribute a: " + readDocument.getAttribute("a"));
System.out.println("Attribute b: " + readDocument.getAttribute("b"));

Jackson JsonNode

The driver internal serde is based on Jackson Databind, therefore the JsonNode class can be used to read and write database documents as well as to map AQL bind variables and query results.

To create a document from Jackson JsonNode:

JsonNode jsonNode = JsonNodeFactory.instance.objectNode()
        .put("_key", "myKey")
        .put("a", "Bar")
        .put("b", 53);
collection.insertDocument(jsonNode);
Commenting on lines +78 to +82

To read a document as Jackson JsonNode:

JsonNode readJsonNode = collection.getDocument("myKey", JsonNode.class);
System.out.println("Key: " + readJsonNode.get("_key").textValue());
System.out.println("Attribute a: " + readJsonNode.get("a").textValue());
System.out.println("Attribute b: " + readJsonNode.get("b").intValue());

Raw JSON strings

The RawJson class can be used to read and write database documents as well as to map AQL bind variables and query results.

To create a document from RawJson:

RawJson json = RawJson.of("""
        {"_key": "myKey", "a": "Baz", "b": 64}
        """);
collection.insertDocument(json);

To read a document as RawJson:

RawJson readJson = collection.getDocument(keyJson, RawJson.class);
System.out.println(readJson.getValue());

 

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