JsonUtil Tutorial

This tutorial provides an overview of the JsonUtil class, which is part of the lightweight-component/aj-util library. The JsonUtil class provides utility methods for working with JSON data in Java applications.

Introduction

The JsonUtil class contains static methods for common JSON operations using Jackson library, including conversion between JSON strings, Java objects, Maps, and Lists.

Main Features

• Convert Java objects to JSON strings (pretty or compact)
• Parse JSON strings into Java objects
• Convert between JSON and Maps/Lists
• Type-safe JSON processing
• Java 8 date/time support
• Strict duplicate detection

Methods

1. Serialization (to JSON)

1. toJson(Object obj) - Convert object to JSON string
2. toJsonPretty(Object obj) - Convert object to pretty-printed JSON

2. Deserialization (from JSON)

1. fromJson(String jsonStr, Class<T> valueType) - Parse JSON to specified type
2. fromJson(String jsonStr, JavaType valueType) - Parse JSON with complex type

3. JSON ↔ Map Conversion

1. json2map(String jsonStr) - JSON to Map<String, Object>
2. json2map(String jsonStr, Class<T> clazz) - JSON to Map with typed values
3. json2sortMap(String jsonStr, Class<T> clazz) - JSON to LinkedHashMap preserving order
4. json2StrMap(String jsonStr) - JSON to Map<String, String>

4. JSON ↔ List Conversion

1. json2list(String jsonArrayStr, Class<T> clazz) - JSON array to List
2. json2mapList(String jsonArrayStr) - JSON array to List

5. Object Conversion

1. convertValue(Object obj, Class<T> clazz) - Convert object types
2. pojo2map(Object obj) - Convert POJO to Map
3. pojo2map(Object obj, Class<T> clazz) - Convert POJO to typed Map
4. map2pojo(Map<String, Object> map, Class<T> clazz) - Convert Map to POJO

6. JSON Tree Model

1. json2Node(String jsonStr) - Parse JSON to JsonNode tree

Usage Examples

Basic Serialization

User user = new User("John", 30);
String json = JsonUtil.toJson(user); 
// {"name":"John","age":30}

String prettyJson = JsonUtil.toJsonPretty(user);
/*
{
  "name" : "John",
  "age" : 30
}
*/

Basic Deserialization

String json = "{\"name\":\"John\",\"age\":30}";
User user = JsonUtil.fromJson(json, User.class);

Map Conversion

Map<String, Object> map = new HashMap<>();
map.put("name", "John");
map.put("age", 30);

String json = JsonUtil.toJson(map);
Map<String, Object> map2 = JsonUtil.json2map(json);

List Conversion

String jsonArray = "[{\"name\":\"John\"}, {\"name\":\"Alice\"}]";
List<User> users = JsonUtil.json2list(jsonArray, User.class);

Configuration

The JsonUtil class is pre-configured with:

• Java 8 date/time support
• Strict duplicate detection
• Asia/Shanghai timezone
• Default ObjectMapper instance

Conclusion

The JsonUtil class provides comprehensive utility methods for working with JSON data, making it easier to serialize, deserialize, and convert between JSON and Java objects.