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How to Convert a JSON String to a Java Object with Jackson?

Barbara Streisand

Release： 2024-11-05 10:48:02

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How to Convert a JSON String to a Java Object with Jackson?

Converting JSON String to Java Object with Jackson

To convert a JSON string to a Java object, Jackson is an open-source Java library widely regarded for its flexibility. In this case, let's explore how to use Jackson to achieve your goal:

The provided JSON string contains a map-like structure with key-value pairs for "libraryname" and a nested list of "mymusic" containing further key-value pairs.

Using Jackson to Convert JSON to Map/List:

<code class="java">ObjectMapper mapper = new ObjectMapper();
Map<String, Object> map = mapper.readValue(jsonString, Map.class);</code>

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This approach treats the JSON as a simple Map, where you can access values using the key, such as:

<code class="java">System.out.println(map.get("libraryname"));
List<Map<String, Object>> songsList = (List<Map<String, Object>>) map.get("mymusic");
System.out.println(songsList.get(0).get("Artist Name"));</code>

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Using Jackson for JSON Tree:

<code class="java">JsonNode rootNode = mapper.readTree(jsonString);</code>

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The JSON Tree approach allows you to access the JSON structure more dynamically:

<code class="java">System.out.println(rootNode.get("libraryname").asText());
JsonNode myMusicArray = rootNode.get("mymusic");
System.out.println(myMusicArray.get(0).get("Artist Name").asText());</code>

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Using Java Pojos (Preferred Approach)

Alternatively, you can define Java Plain Old Java Objects (POJOs) to represent your JSON structure:

<code class="java">public class Library {
    @JsonProperty("libraryname")
    private String name;
    @JsonProperty("mymusic")
    private List<Song> songs;
}
public class Song {
    @JsonProperty("Artist Name")
    private String artistName;
    @JsonProperty("Song Name")
    private String songName;
}

ObjectMapper mapper = new ObjectMapper();
Library library = mapper.readValue(jsonString, Library.class);</code>

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This method allows you to access the data in a more object-oriented manner:

<code class="java">System.out.println(library.getName());
List<Song> songs = library.getSongs();
System.out.println(songs.get(0).getArtistName());</code>

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