如何使用Jackson和JSON Pointer查询解析任何JSON节点
作者：梦想画家
本文介绍了JSON Pointer是字符串表达式，可以非常方便解析复杂JSON节点值，具有很好的参考价值，希望对大家有所帮助。如有错误或未考虑完全的地方，望不吝赐教
Jackson和JSON Pointer查询解析任何JSON节点
JSON Pointer是字符串表达式，用于标识JSON文档特定节点。RFC 6901规范有定义，用于查询复杂Json文档结构。
1.示例Json文档
{
"firstName": "John",
"lastName": "Doe",
"address": {
"street": "21 2nd Street",
"city": "New York",
"postalCode": "10021-3100",
"coordinates": {
"latitude": 40.7250387,
"longitude": -73.9932568
}
},
"phone": [
"139",
"137"
],
"grade": [
{
"name": "math",
"score": 99
},
{
"name": "english",
"score": 97
}
]
}
该文档包括复杂的嵌套，其中嵌套类型有对象，数组，数组对象。下面使用JSON Pointer进行解析。
2. 解析文档
使用Jackson的核心对象ObjectMapper，首先解析json字符串未JsonNode。
String json = "{\n" +
" \"firstName\": \"John\",\n" +
" \"lastName\": \"Doe\",\n" +
" \"address\": {\n" +
" \"street\": \"21 2nd Street\",\n" +
" \"city\": \"New York\",\n" +
" \"postalCode\": \"10021-3100\",\n" +
" \"coordinates\": {\n" +
" \"latitude\": 40.7250387,\n" +
" \"longitude\": -73.9932568\n" +
" }\n" +
" },\n" +
" \"phone\":[\"139\",\"137\"],\n" +
" \"grade\":[\n" +
" {\"name\":\"math\",\"score\":99},\n" +
" {\"name\":\"english\",\"score\":97}\n" +
" ]\n" +
" }";
ObjectMapper mapper = new ObjectMapper();
JsonNode node = mapper.readTree(json);
2.1 获取属性
JsonNode firstName = node.at("/firstName");
print("firstName",firstName.toString());
必须以/开头，表示当前起始节点。
输出结果：
firstName:"John"
2.2 获取对象属性
JsonNode coordinatesNode = node.at("/address/coordinates");
print("coordinatesNode",coordinatesNode.toString());
输出结果：
coordinatesNode:{"latitude":40.7250387,"longitude":-73.9932568}
2.3 获取数组属性
JsonNode phoneNode = node.at("/phone");
print("phoneNode", phoneNode.toString());
输出结果：
phoneNode:["139","137"]
2.4 获取数组属性元素
JsonNode phone1Node = node.at("/phone/0");
print("phone1Node",phone1Node.toString());
输出结果：
phone1Node:"139"
2.4 获取数组对象属性
JsonNode nameNode = node.at("/grade/0/name");
print("name",nameNode.toString());
JsonNode scoreNode = node.at("/grade/0/score");
print("score",scoreNode.toString());
输出结果：
name:"math"
score:99
Jackson 通用解析JSON方法
package com.util;
import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.type.TypeFactory;
import com.google.common.collect.Lists;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* json 解析类，通用于全项目
* <p/>
* Created by 刘一波 on 15/7/24.
* E-Mail:zhanlanstar@163.com
*/
@Slf4j
public class JsonUtils {
private static ObjectMapper objectMapper = new ObjectMapper();
static {
objectMapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
objectMapper.configure(SerializationFeature.INDENT_OUTPUT, true);
objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
objectMapper.setDateFormat(sdf);
}
/**
* 提供给elasticsearch使用，把bean转换成list map 集合类型，否则不能存入索引
*
* @param o
* @return
*/
public static Object beanToJsonObject(Object o) {
return jsonStrToList(objectToJsonStr(o), Map.class);
}
public static String objectToJsonStr(Object o) {
try {
return objectMapper.writeValueAsString(o);
} catch (IOException e) {
log.error("object can not objectTranslate to json", e);
}
return null;
}
public static <T> T jsonStrToObject(String json, Class<T> cls) {
try {
return objectMapper.readValue(json, cls);
} catch (IOException e) {
log.error("json cant be objectTranslate to object", e);
return null;
}
}
public static <T> T jsonDataToObject(String jsonStr, Class<T> cls) {
if (!StringUtils.isEmpty(jsonStr)) {
T data = JsonUtils.jsonStrToObject(jsonStr, cls);
return data;
} else {
return null;
}
}
public static <T> List<T> jsonStrToList(String jsonStr, Class<?> clazz) {
List<T> list = Lists.newArrayList();
try {
// 指定容器结构和类型（这里是ArrayList和clazz）
TypeFactory t = TypeFactory.defaultInstance();
list = objectMapper.readValue(jsonStr,
t.constructCollectionType(ArrayList.class, clazz));
} catch (IOException e) {
log.error("反序列化序列化attributes，从Json到List报错", e);
}
return list;
}
public static Map jsonStrToMap(String attributes) {
try {
return objectMapper.readValue(attributes, HashMap.class);
} catch (IOException e) {
log.error("反序列化序列化attributes，从Json到HashMap报错", e);
}
return new HashMap();
}
}
以上为个人经验，希望能给大家一个参考，也希望大家多多支持脚本之家。