使用json-path解析json

客官°小女子只卖身不卖艺 2024-02-19 18:41 50阅读 0赞

在我们的日常开发中，有时候需要从一个json字符串中获取一个值，或者从一段json字符串中获取到某些值，如果先使用Gson或Jackson转换成java对象在获取值，有些时候是很麻烦的，那么有没有一种根据表达式提取json中的数据的方式呢，就像使用xpath语法操作xml文件一样，答案是有的,**jsonPath**就是这样的一个在java中操作json的简单工具。

jsonPath的在github上的网址如下：[https://github.com/json-path/JsonPath][https_github.com_json-path_JsonPath]

**一、json-path中的操作符**  
![aHR0cDovL2RsMi5pdGV5ZS5jb20vdXBsb2FkL2F0dGFjaG1lbnQvMDEyOC8zNDUyL2RkZjUyZGY5LThhZTMtMzdiMy1iNjJhLWM0NGNhNjMzNDE3Ny5wbmc][]

**二、json-path中可以使用的函数**  
![aHR0cDovL2RsMi5pdGV5ZS5jb20vdXBsb2FkL2F0dGFjaG1lbnQvMDEyOC8zNDU0LzNlZDE2YWQ3LTVhNTEtMzBmYi05NGMxLWQ4NGQ3OGI2MTAxNy5wbmc][]

**三、过滤操作符**  
![aHR0cDovL2RsMi5pdGV5ZS5jb20vdXBsb2FkL2F0dGFjaG1lbnQvMDEyOC8zNDU2Lzc0ZWViMzM5LWM3NWUtMzcyOS1iMjU5LWUxOWUxYmVjYTA2Yy5wbmc][]  
 **四、表达式使用示例：**

1、数据准备

{
        "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
    }

2、示例代码

![aHR0cDovL2RsMi5pdGV5ZS5jb20vdXBsb2FkL2F0dGFjaG1lbnQvMDEyOC8zNDU4LzI4MGE4MzA2LWFkZjctM2RjOC05MjQwLWY1YzNmYjVlZDRhYy5wbmc][]  
 **五、在JAVA代码中使用**

1、pom.xml文件中引入json-path的依赖

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

2、编写代码

package com.huan.json;
    
    import java.io.BufferedReader;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    import java.util.List;
    import java.util.Map;
    
    import com.jayway.jsonpath.Configuration;
    import com.jayway.jsonpath.JsonPath;
    import com.jayway.jsonpath.Option;
    import com.jayway.jsonpath.spi.json.JsonProvider;
    
    /**
     * 测试jsonpath的使用
     * 
     * @描述
     * @作者 huan
     * @时间 2017年12月31日 - 下午4:34:11
     */
    public class JsonPathTest {
    	public static void main(String[] args) {
    		String json = readJson();
    		Configuration configuration = Configuration.defaultConfiguration();
    		configuration = configuration.addOptions(//
    				Option.DEFAULT_PATH_LEAF_TO_NULL, // 如果路径不存在则返回null,而不要抛出PathNotFoundException
    				Option.SUPPRESS_EXCEPTIONS // 抑制异常的抛出，当设置了Option.ALWAYS_RETURN_LIST时返回[],否则返回null
    		);
    		// 如果项目中存在gson则此处可以new 一个GsonJsonProvider，那么返回对象
    		// configuration.jsonProvider(new GsonJsonProvider());
    		JsonProvider jsonProvider = configuration.jsonProvider();
    		/**
    		 * 此处预先解析json,默认请情下JsonPath.read方法每掉一次都会重新解析json，此处预先解析好就不用每次都进行解析
    		 */
    		Object document = jsonProvider.parse(json);
    		// 1.获取所有book中的author
    		List<String> authors = JsonPath.read(document, "$.store.book[*].author");
    		System.out.println(authors);
    		// 2.获取价格比$.expensive大的书籍
    		List<Map<String, Object>> books = JsonPath.read(document, "$.store.book[?(@.price > $.expensive)]");
    		System.out.println(books);
    		// 3.输出一个不存在的表达式,因为存在这个选项的配置，所有返回的是Option.DEFAULT_PATH_LEAF_TO_NULL
    		Object notExistsValue = JsonPath.using(configuration).parse(document).read("$.not-exists-path.path");
    		System.out.println(notExistsValue);
    		// 4.存在多级属性缺失
    		Object object = JsonPath.using(configuration).parse(document).read("$.not-exists.path");
    		System.out.println(object);
    	}
    
    	public static String readJson() {
    		StringBuilder builder = new StringBuilder();
    		try (InputStream is = JsonPathTest.class.getResourceAsStream("data.json"); InputStreamReader isr = new InputStreamReader(is); BufferedReader br = new BufferedReader(isr);) {
    			String line;
    			while (null != (line = br.readLine())) {
    				builder.append(line);
    			}
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    		return builder.toString();
    	}
    
    }

3、结果  
![aHR0cDovL2RsMi5pdGV5ZS5jb20vdXBsb2FkL2F0dGFjaG1lbnQvMDEyOC8zNDYwLzZlZGQ1ZDgyLTgzZGUtM2RhNi04YjJkLTM3ZTAzOGNiOTA0MS5wbmc][]

**六、注意事项：**

1、在json-path的filter中 1 和 '1' 是不相等的。

2、filter中的字符串需要使用单引号或双引号括起来

3、JsonPath.read方法会每次进行json的解析，解决思路就是预先解析json

4、Option中提供了一些枚举值可以控制解析的结果返回

5、如果不想使用默认的JsonProvider则可以自己提供一个。

**七、完整的思维导图见附件中。**

[https_github.com_json-path_JsonPath]: https://github.com/json-path/JsonPath
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