Jackson

Jackson

<dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>${jackson}</version>
</dependency>

Json 读取有两种模式:

1. JSON Tree Model
   1. 树的根代表整个JSON文档。
   2. 树中的每个节点对应于JSON值，如对象、数组、字符串、数字、布尔值或空值。
   3. 节点可以有子节点，表示嵌套的JSON结构。
2. Data-binding method
   1. 直接转换成对象

try {ObjectMapper mapper = new ObjectMapper();// tree modelJsonNode rootNode = mapper.readTree(json);JsonNode appleNode = rootNode.path("a").path("b").path("c");// data-bindingApple apple = mapper.treeToValue(appleNode, Apple.class);
} catch (Exception e) {e.printStackTrace();
}

JSON Tree Model

1. readTree
2. path
3. findValue
4. findPath
5. asText
6. isEmpty
7. isArray
8. iterator (foreach)
9. treeToValue

Data-binding method (注解方法)

@Data
@JacksonXmlRootElement(localName = "xBody")
public class Body {@JacksonXmlProperty(isAttribute = true)private String     version;@JacksonXmlProperty(localName = "total")@JsonInclude(JsonInclude.Include.NON_NULL)private Integer    total;@JacksonXmlProperty(localName = "item")@JsonProperty("item")@JacksonXmlElementWrapper(localName = "list")private List<Item> itemList;@JacksonXmlProperty(localName = "order")@JacksonXmlElementWrapper(useWrapping = false)private List<Order> orders;@Datapublic static class Item {@JacksonXmlPropertyprivate String name;}
}

• 注解簇
  

Spring 自带 Json 工厂

JsonNode 转 Map

使用 springboot 提供的 json 转换工具 org.springframework.boot.json.JsonParserFactory

private static Map<String, Object> setAllValue(JsonNode source, BillSubData target) {JsonParser jsonParser = JsonParserFactory.getJsonParser();Map<String, Object> sourceMap = jsonParser.parseMap(source.toString());for (Map.Entry<String, Object> entry : sourceMap.entrySet()) {target.set(entry.getKey(), entry.getValue());}return sourceMap;
}

JsonNode 判断 null

// Method similar to #findValue(str), 
// but that will return a "missing node" instead of null if no field is found. 
// Missing node is a specific kind of node for which isMissingNode returns true;
JsonNode node = jsonNode.findPath("key"); // 必须使用 findPath 获取 JsonNode 对象if (node.isNull()) {// 节点为空
}
if (node.isEmpty()) {// 节点为空（null、空对象、空数组）
}
if (node.isMissingNode()) {// 是否为缺失节点（不存在于 JSON 结构中）
}