Jackson
xml
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>${jackson}</version>
</dependency>
Json 读取有两种模式:
- JSON Tree Model
- 树的根代表整个JSON文档。
- 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。
- 节点可以有子节点,表示嵌套的JSON结构。
- Data-binding method
- 直接转换成对象
java
try {
ObjectMapper mapper = new ObjectMapper();
// tree model
JsonNode rootNode = mapper.readTree(json);
JsonNode appleNode = rootNode.path("a").path("b").path("c");
// data-binding
Apple apple = mapper.treeToValue(appleNode, Apple.class);
} catch (Exception e) {
e.printStackTrace();
}
JSON Tree Model
- readTree
- path
- findValue
- findPath
- asText
- isEmpty
- isArray
- iterator (foreach)
- treeToValue
Data-binding method (注解方法)
java
@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;
@Data
public static class Item {
@JacksonXmlProperty
private 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
java
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
java
// 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)
}