How to Convert JSON Strings to Maps with Jackson JSON?

Converting JSON Strings to Maps with Jackson JSON

Jackson JSON is a popular Java library for converting JSON strings to various data structures. However, encountering an unchecked assignment error while attempting to convert JSON to a Map could be frustrating.

To resolve this issue, follow these steps:

1. Use TypeReference:

   <code class="java">TypeReference<HashMap<String, String>> typeRef
           = new TypeReference<HashMap<String, String>>() {};
   
   HashMap<String, String> propertyMap = mapper.readValue(properties, typeRef);</code>

2. Use Generic JsonNode:

   <code class="java">JsonNode rootNode = mapper.readTree(properties);
   
   if (rootNode.isObject()) {
       Map<String, String> propertyMap = new HashMap<>();
       rootNode.fields().forEachRemaining(field -> propertyMap.put(field.getKey(), field.getValue().asText()));
   }</code>

For native Java JSON conversion, you can explore JSON.org. In addition, here's how to achieve similar JSON decoding functionality in Jackson:

<code class="java">ObjectNode albumList = mapper.createObjectNode();

ArrayNode albums = mapper.createArrayNode();
albums.add(mapper.createObjectNode().put("title", "Album 1"));
albums.add(mapper.createObjectNode().put("title", "Album 2"));

albumList.put("albums", albums);

System.out.println(albumList);</code>

This generates a JSON object with an array of albums, providing the same functionality as PHP's json_decode($str).

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