Java之JSON操作（Jackson）

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Java to JSON：

 1 package json.jackson; 2  3 import bean.User; 4 import com.fasterxml.jackson.databind.ObjectMapper; 5  6 import java.io.File; 7 import java.util.Map; 8  9 /**10  * Jackson – Java to JSON11  * 功能：JSON與Java對象、Map等類型轉換，JSON檔案的讀寫等12  * 依賴包：jackson-databind-2.8.11.1.jar、jackson-core-2.8.10.jar、jackson-annotations-2.8.0.jar13  * https://github.com/FasterXML/jackson-databind14  */15 public class JavaToJSON {16     public static void main(String[] ars) throws Exception {17         User user = new User("tom", 25, "NO.1 street");18         ObjectMapper objectMapper = new ObjectMapper();19 20         // Java對象轉json，也支援bytes21         String json = objectMapper.writeValueAsString(user);22         System.out.println("Java對象轉json:" + json);23 24         // json轉Java對象25         User user2 = objectMapper.readValue(json, User.class);26         System.out.println("json轉Java對象" + user2);27 28         // 讀檔案29         String jsonFilePath = "src/main/java/json/jackson/JsonReader.json";30         User user3 = objectMapper.readValue(new File(jsonFilePath), User.class);31         System.out.println("讀取JSON檔案：" + user3);32         // 寫檔案33         objectMapper.writeValue(new File(jsonFilePath), user3);34 35         // json轉map，也支援List36         Map map = objectMapper.readValue(json, Map.class);37         System.out.println("json轉map：" + map);38 39         // map轉json字串，支援所有類型轉字串40         String json2 = objectMapper.writeValueAsString(map);41         System.out.println("map轉json:" + json2);42 43     }44 }

JsonNode：

 1 package json.jackson; 2  3 import com.fasterxml.jackson.databind.JsonNode; 4 import com.fasterxml.jackson.databind.ObjectMapper; 5  6 import java.io.File; 7 import java.util.List; 8  9 /**10  * JsonNode11  * 處理複雜的JSON，返回多個對象的情況12  * 從檔案中讀取複雜的JSON，根據key找到對應value值13  * 依賴包：jackson-databind-2.8.11.1.jar、jackson-core-2.8.10.jar、jackson-annotations-2.8.0.jar14  * https://github.com/FasterXML/jackson-databind15  */16 public class JSONTreeDemo {17     public static void main(String[] ars) throws Exception {18         ObjectMapper objectMapper = new ObjectMapper();19         String jsonFilePath = "src/main/java/json/jackson/Json2.json";20         // 以樹形態支援多個物件的情況：支援讀取多種類型21         JsonNode jsonNode = objectMapper.readTree(new File(jsonFilePath));22         System.out.println("jsonNode：" + jsonNode);23         // 根據key查詢多個值，返回list24         List<JsonNode> list = jsonNode.findValues("name");25         System.out.println("Values：" + list);26 27         // 根據key查詢單個值28         String channel = jsonNode.get("channel").asText();29         System.out.println("查詢channel的值：" + channel);30     }31 }

 

Java之JSON操作（Jackson）