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| 1 | +package util; |
| 2 | + |
| 3 | +import com.fasterxml.jackson.databind.JavaType; |
| 4 | +import com.fasterxml.jackson.databind.ObjectMapper; |
| 5 | +import com.fasterxml.jackson.databind.type.TypeFactory; |
| 6 | +import com.fasterxml.jackson.databind.util.StdDateFormat; |
| 7 | + |
| 8 | +import java.io.IOException; |
| 9 | +import java.nio.file.Files; |
| 10 | +import java.nio.file.Path; |
| 11 | +import java.nio.file.StandardOpenOption; |
| 12 | + |
| 13 | +/** |
| 14 | + * The JsonUtils class provides a simple interface for writing and reading JSON files |
| 15 | + * |
| 16 | + * @author <a href="mailto:[email protected]">Gabriel Skoglund</a> |
| 17 | + */ |
| 18 | +public class JsonUtils { |
| 19 | + |
| 20 | + /** The default JSON file ending ".json" */ |
| 21 | + public static final String JSON_FILE_ENDING = ".json"; |
| 22 | + |
| 23 | + /** The string representing an empty JSON object */ |
| 24 | + public static final String EMPTY_JSON_OBJECT = "{}"; |
| 25 | + |
| 26 | + private static final ObjectMapper mapper = |
| 27 | + new ObjectMapper().setDateFormat(new StdDateFormat()); |
| 28 | + |
| 29 | + private JsonUtils() { /* Nothing to see here... */ } |
| 30 | + |
| 31 | + /** |
| 32 | + * Read a JSON object from file |
| 33 | + * @param file the path to the JSON file to read. |
| 34 | + * @param jsonType the type that the data should be considered as. |
| 35 | + * @return an object of the specified type as read from the given file. |
| 36 | + */ |
| 37 | + public static <T> T readFromFile(Path file, Class<T> jsonType) { |
| 38 | + try { |
| 39 | + return mapper.readValue(Files.readString(file), jsonType); |
| 40 | + } catch (IOException e) { |
| 41 | + throw new RuntimeException(e); |
| 42 | + } |
| 43 | + } |
| 44 | + |
| 45 | + /** |
| 46 | + * Read a JSON object from file |
| 47 | + * @param file the path to the JSON file to read. |
| 48 | + * @param jsonType the type that the data should be considered as. |
| 49 | + * @return an object of the specified type as read from the given file. |
| 50 | + */ |
| 51 | + public static <T> T readFromFile(Path file, JavaType jsonType) { |
| 52 | + try { |
| 53 | + return mapper.readValue(Files.readString(file), jsonType); |
| 54 | + } catch (IOException e) { |
| 55 | + throw new RuntimeException(e); |
| 56 | + } |
| 57 | + } |
| 58 | + |
| 59 | + /** |
| 60 | + * Read a JSON object from file which can be empty |
| 61 | + * @param file the path to the JSON file to read which can be empty. |
| 62 | + * @param jsonType the type that the data should be considered as. |
| 63 | + * @return an object of the specified type as read from the given file. |
| 64 | + */ |
| 65 | + public static <T> T readFromNullableFile(Path file, JavaType jsonType) { |
| 66 | + try { |
| 67 | + if (Files.readString(file).isEmpty()) { |
| 68 | + // Handle empty JSON file. |
| 69 | + return null; |
| 70 | + } else { |
| 71 | + return mapper.readValue(Files.readString(file), jsonType); |
| 72 | + } |
| 73 | + } catch (IOException e) { |
| 74 | + throw new RuntimeException(e); |
| 75 | + } |
| 76 | + } |
| 77 | + |
| 78 | + /** |
| 79 | + * Write an object to a JSON file. |
| 80 | + * @param outputFilePath the file path where the data should be written. |
| 81 | + * @param data the object to be stored as JSON. |
| 82 | + */ |
| 83 | + public static void writeToFile(Path outputFilePath, Object data) { |
| 84 | + try { |
| 85 | + String json = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(data); |
| 86 | + Files.writeString(outputFilePath, json, StandardOpenOption.WRITE, StandardOpenOption.CREATE, |
| 87 | + StandardOpenOption.TRUNCATE_EXISTING); |
| 88 | + } catch (IOException e) { |
| 89 | + throw new RuntimeException(e); |
| 90 | + } |
| 91 | + } |
| 92 | + |
| 93 | + /** |
| 94 | + * @return a {@link TypeFactory} from the underlying {@link ObjectMapper}. |
| 95 | + */ |
| 96 | + public static TypeFactory getTypeFactory() { |
| 97 | + return mapper.getTypeFactory(); |
| 98 | + } |
| 99 | +} |
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