引言

假设想要解析JSON对象且JSON的格式不固定，最开始的做法是转换Json对象为Map对象，然后一层层遍历Map（例如使用Gson），那么有没有类似XML中的xpath解析表达式的工具？最终发现了json-path工具。
参考链接：github json-path
Maven依赖：

 <dependency>
    <groupId>com.jayway.jsonpath</groupId>
    <artifactId>json-path</artifactId>
    <version>2.4.0</version>
</dependency>

该工具提供了类似XPATH的层级似的JSON解析功能，同时提供读取、写入的功能。

JsonPath语法

Operators

Functions

Functions can be invoked at the tail end of a path - the input to a function is the output of the path expression.
The function output is dictated by the function itself.

Filter Operators

Filters are logical expressions used to filter arrays. A typical filter would be [?(@.age > 18)] where @ represents the current item being processed. More complex filters can be created with logical operators && and ||. String literals must be enclosed by single or double quotes ([?(@.color == ‘blue’)] or [?(@.color == “blue”)]).

JsonPath语法示例

Given the json

{
    "store": {
        "book": [
            {
                "category": "reference",
                "author": "Nigel Rees",
                "title": "Sayings of the Century",
                "price": 8.95
            },
            {
                "category": "fiction",
                "author": "Evelyn Waugh",
                "title": "Sword of Honour",
                "price": 12.99
            },
            {
                "category": "fiction",
                "author": "Herman Melville",
                "title": "Moby Dick",
                "isbn": "0-553-21311-3",
                "price": 8.99
            },
            {
                "category": "fiction",
                "author": "J. R. R. Tolkien",
                "title": "The Lord of the Rings",
                "isbn": "0-395-19395-8",
                "price": 22.99
            }
        ],
        "bicycle": {
            "color": "red",
            "price": 19.95
        }
    },
    "expensive": 10
}

JsonPath代码示例

解析并修改如下JSON（示例为Istio中的某个VirtualService定义）：

{
  "kind": "VirtualService",
  "apiVersion": "networking.istio.io/v1alpha3",
  "metadata": {
    "name": "my-svc",
    "namespace": "tsp"
  },
  "spec": {
    "hosts": [
      "s106.tsp.svc.cluster.local",
      "my-svc.tsp.svc.cluster.local"
    ],
    "gateways": [
      "mesh",
      "my-svc"
    ],
    "http": [
      {
        "match": [
          {
            "headers": {
              "user-id": {
                "regex": "11|22|33"
              }
            },
            "uri": {
              "prefix": "/256"
            }
          }
        ],
        "rewrite": {
          "uri": "/my_svc"
        },
        "route": [
          {
            "destination": {
              "host": "s106.tsp.svc.cluster.local",
              "subset": "v257"
            }
          }
        ]
      },
      {
        "match": [
          {
            "uri": {
              "prefix": "/256"
            }
          }
        ],
        "rewrite": {
          "uri": "/my_svc"
        },
        "route": [
          {
            "destination": {
              "host": "s106.tsp.svc.cluster.local",
              "subset": "v256"
            }
          }
        ]
      },
      {
        "route": [
          {
            "destination": {
              "host": "s106.tsp.svc.cluster.local",
              "subset": "v256"
            }
          }
        ]
      }
    ],
    "tcp": null,
    "tls": null
  }
}

import com.jayway.jsonpath.DocumentContext;
import com.jayway.jsonpath.Filter;
import com.jayway.jsonpath.JsonPath;
import com.svc.mgt.utils.JsonUtils;
import net.minidev.json.JSONArray;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PowerMockIgnore;
import org.powermock.modules.junit4.PowerMockRunner;

import java.util.Map;

import static com.jayway.jsonpath.Criteria.where;
import static com.jayway.jsonpath.Filter.filter;

/**
 * K8s查询结果Json转换 - 测试
 *
 * @Ahthor luohq
 * @Date 2020-07-20
 */

@RunWith(PowerMockRunner.class)  //使用PowerMockRunner运行时
@PowerMockIgnore({"javax.management.*"}) //忽略一些mock异常
public class K8sJsonResultTest {
    private static final Logger logger = LogManager.getLogger(K8sJsonResultTest.class);
    @Test
    public void testVsJson() {
        String vsResult = "...";
        /** JsonPath解析 */
        final DocumentContext ctx = JsonPath.parse(vsResult);
        
        /** 基础路由过滤器 - 包含http[].match 且 不包含有http[].match[0].headers*/
        Filter baseRouteFilter = filter(
                where("$.match").exists(true).and("$.match[0].headers").exists(false)
        );

        /** 读取属性（指定过滤器）*/
        JSONArray httpRoutes = ctx.read("$.spec.http[?]*", baseRouteFilter);
        for (Object httpRoute : httpRoutes) {
            String subset = JsonPath.read(httpRoute, "$.route[0].destination.subset");
            logger.info("baseRoute -> subset={}, httpRoute={}", subset, JsonPath.parse(httpRoute).jsonString());
        }
        /** 读取属性 */
        Map httpRouteObj = ctx.read("$.spec.http[0]");
        
        //替换user-id | product-id
        String headersJson = String.format("{\"user-id\": {\"regex\": \"%s\"},\"product-id\": {\"exact\":\"%s\"}}", "111|222", "12342");
        /** 设置属性 - 重置baseRoute中的match.headers（add添加数组元素、set设置属性、put新增或修改属性） */
        JsonPath.parse(httpRouteObj).put("$.match[0]", "headers", JsonUtils.fromJson(headersJson, Map.class));
        logger.info("svcRouteRule: {}", JsonPath.parse(httpRouteObj).jsonString());
        logger.info("vs.ctx={}", ctx.jsonString());

        /** 删除对象 - 清空 $.spec.http数组 */
        ctx.delete("$.spec.http.*");
        logger.info("vs.ctx={}", ctx.jsonString());

    }
    
}

运行结果：

2020-07-21 14:49:39.389 INFO [main][K8sJsonResultTest.java:146] - baseRoute -> subset=v256, httpRoute={"match":[{"uri":{"prefix":"/256"}}],"rewrite":{"uri":"/mx_tour_app"},"route":[{"destination":{"host":"s106.tsp.svc.cluster.local","subset":"v256"}}]}
2020-07-21 14:49:39.488 INFO [main][K8sJsonResultTest.java:154] - svcRouteRule: {"match":[{"headers":{"user-id":{"regex":"111|222"},"product-id":{"exact":"12342"}},"uri":{"prefix":"/256"}}],"rewrite":{"uri":"/mx_tour_app"},"route":[{"destination":{"host":"s106.tsp.svc.cluster.local","subset":"v257"}}]}
2020-07-21 14:49:39.488 INFO [main][K8sJsonResultTest.java:155] - vs.ctx={"kind":"VirtualService","apiVersion":"networking.istio.io/v1alpha3","metadata":{"name":"my-app","namespace":"tsp","selfLink":"/apis/networking.istio.io/v1alpha3/namespaces/tsp/virtualservices/my-app","uid":"368f02de-ac7b-11ea-b7d7-fa163e432d7e","resourceVersion":"194978865","generation":11,"creationTimestamp":"2020-06-12T07:06:18Z"},"spec":{"hosts":["s106.tsp.svc.cluster.local","my-app.tsp.svc.cluster.local","my-app-pre.xxxx.com"],"gateways":["mesh","my-app"],"http":[{"match":[{"headers":{"user-id":{"regex":"111|222"},"product-id":{"exact":"12342"}},"uri":{"prefix":"/256"}}],"rewrite":{"uri":"/mx_tour_app"},"route":[{"destination":{"host":"s106.tsp.svc.cluster.local","subset":"v257"}}]},{"match":[{"uri":{"prefix":"/256"}}],"rewrite":{"uri":"/mx_tour_app"},"route":[{"destination":{"host":"s106.tsp.svc.cluster.local","subset":"v256"}}]},{"route":[{"destination":{"host":"s106.tsp.svc.cluster.local","subset":"v256"}}]}],"tcp":null,"tls":null}}
2020-07-21 14:49:39.489 INFO [main][K8sJsonResultTest.java:160] - vs.ctx={"kind":"VirtualService","apiVersion":"networking.istio.io/v1alpha3","metadata":{"name":"my-app","namespace":"tsp","selfLink":"/apis/networking.istio.io/v1alpha3/namespaces/tsp/virtualservices/my-app","uid":"368f02de-ac7b-11ea-b7d7-fa163e432d7e","resourceVersion":"194978865","generation":11,"creationTimestamp":"2020-06-12T07:06:18Z"},"spec":{"hosts":["s106.tsp.svc.cluster.local","my-app.tsp.svc.cluster.local","my-app-pre.xxxx.com"],"gateways":["mesh","my-app"],"http":[],"tcp":null,"tls":null}}

本文地址：https://blog.csdn.net/luo15242208310/article/details/107487627