json-path/JsonPath

官方地址：https://github.com/json-path/JsonPath

JsonPath提供的json解析非常强大，它提供了类似正则表达式的语法，基本上可以满足所有你想要获得的json内容。下面我把官网介绍的每个表达式用代码实现，可以更直观的知道该怎么用它。

一.首先需要依赖的jar包

二.因为编译的时候会报log4j的警报，所以需要在项目的src目录下新建log4j.properties文件，内容如下：
log4j.rootLogger=WARN, stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - %m%n

三.准备一个json文本

{
    "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
}

四.我们从代码中分析用法，代码如下

package com.jsonpath;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import net.minidev.json.JSONArray;

import com.jayway.jsonpath.Configuration;
import com.jayway.jsonpath.JsonPath;
import com.jayway.jsonpath.ReadContext;

/** 
 * @author QiaoJiafei 
 * @version 创建时间：2016年3月2日 下午3:37:42 
 * 类说明 
 */
public class TestJsonPath {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String sjson = readtxt();
        //String sjson = "{\"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}";
        /*
        print("--------------------------------------getJsonValue0--------------------------------------");
        getJsonValue0(sjson);
        print("--------------------------------------getJsonValue1--------------------------------------");
        getJsonValue1(sjson);
        print("--------------------------------------getJsonValue2--------------------------------------");
        getJsonValue2(sjson);
        print("--------------------------------------getJsonValue3--------------------------------------");
        getJsonValue3(sjson);
        print("--------------------------------------getJsonValue4--------------------------------------");
        getJsonValue4(sjson);
        */
        
        print("--------------------------------------getJsonValue--------------------------------------");
        getJsonValue(sjson);
    }

    private static String readtxt() {
        // TODO Auto-generated method stub
        StringBuilder sb = new StringBuilder();
        try {
            FileReader fr = new FileReader("D:/workspace/PressureTest/json.txt");
            BufferedReader bfd = new BufferedReader(fr);
            String s = "";
            while((s=bfd.readLine())!=null) {
                sb.append(s);
            }
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println(sb.toString());
        return sb.toString();
    }
    
    private static void getJsonValue(String json) {
        //The authors of all books：获取json中store下book下的所有author值
        List<String> authors1 = JsonPath.read(json, "$.store.book[*].author");
        
        //All authors：获取所有json中所有author的值
        List<String> authors2 = JsonPath.read(json, "$..author");
        
        //All things, both books and bicycles //authors3返回的是net.minidev.json.JSONArray：获取json中store下的所有value值，不包含key，如key有两个，book和bicycle
        List<Object> authors3 = JsonPath.read(json, "$.store.*");
        
        
        //The price of everything：获取json中store下所有price的值
        List<Object> authors4 = JsonPath.read(json, "$.store..price");
        
        //The third book：获取json中book数组的第3个值
        List<Object> authors5 = JsonPath.read(json, "$..book[2]");
        
        //The first two books：获取json中book数组的第1和第2两个个值
        List<Object> authors6 = JsonPath.read(json, "$..book[0,1]");
        
        //All books from index 0 (inclusive) until index 2 (exclusive)：获取json中book数组的前两个区间值
        List<Object> authors7 = JsonPath.read(json, "$..book[:2]");
        
        //All books from index 1 (inclusive) until index 2 (exclusive)：获取json中book数组的第2个值
        List<Object> authors8 = JsonPath.read(json, "$..book[1:2]");
        
        //Last two books：获取json中book数组的最后两个值
        List<Object> authors9 = JsonPath.read(json, "$..book[-2:]");
        
        //Book number two from tail：获取json中book数组的第3个到最后一个的区间值
        List<Object> authors10 = JsonPath.read(json, "$..book[2:]");
        
        //All books with an ISBN number：获取json中book数组中包含isbn的所有值
        List<Object> authors11 = JsonPath.read(json, "$..book[?(@.isbn)]");
        
        //All books in store cheaper than 10：获取json中book数组中price<10的所有值
        List<Object> authors12 = JsonPath.read(json, "$.store.book[?(@.price < 10)]");
        
        //All books in store that are not "expensive"：获取json中book数组中price<=expensive的所有值
        List<Object> authors13 = JsonPath.read(json, "$..book[?(@.price <= $['expensive'])]");
        
        //All books matching regex (ignore case)：获取json中book数组中的作者以REES结尾的所有值（REES不区分大小写）
        List<Object> authors14 = JsonPath.read(json, "$..book[?(@.author =~ /.*REES/i)]");
        
        //Give me every thing：逐层列出json中的所有值，层级由外到内
        List<Object> authors15 = JsonPath.read(json, "$..*");
        
        //The number of books：获取json中book数组的长度
        List<Object> authors16 = JsonPath.read(json, "$..book.length()");
        print("**************authors1**************");
        print(authors1);
        print("**************authors2**************");
        print(authors2);
        print("**************authors3**************");
        printOb(authors3);
        print("**************authors4**************");
        printOb(authors4);
        print("**************authors5**************");
        printOb(authors5);
        print("**************authors6**************");
        printOb(authors6);
        print("**************authors7**************");
        printOb(authors7);
        print("**************authors8**************");
        printOb(authors8);
        print("**************authors9**************");
        printOb(authors9);
        print("**************authors10**************");
        printOb(authors10);
        print("**************authors11**************");
        printOb(authors11);
        print("**************authors12**************");
        printOb(authors12);
        print("**************authors13**************");
        printOb(authors13);
        print("**************authors14**************");
        printOb(authors14);
        print("**************authors15**************");
        printOb(authors15);
        print("**************authors16**************");
        printOb(authors16);
        
    }

    /**
     * 读取json的一种写法，得到匹配表达式的所有值
     * */
    private static void getJsonValue0(String json) {
        // TODO Auto-generated method stub
        List<String> authors = JsonPath.read(json, "$.store.book[*].author");
        //System.out.println(authors.size());
        print(authors);
        
    }
    
    /**
     * 读取json的一种写法，得到某个具体值
     * */
    private static void getJsonValue1(String json) {
        Object document = Configuration.defaultConfiguration().jsonProvider().parse(json);

        String author0 = JsonPath.read(document, "$.store.book[0].author");
        String author1 = JsonPath.read(document, "$.store.book[1].author");
        print(author0);
        print(author1);
        
    }
    
    /**
     * 读取json的一种写法
     * */
    private static void getJsonValue2(String json) {
        ReadContext ctx = JsonPath.parse(json);

        List<String> authorsOfBooksWithISBN = ctx.read("$.store.book[?(@.isbn)].author");


        List<Map<String, Object>> expensiveBooks = JsonPath
                                    .using(Configuration.defaultConfiguration())
                                    .parse(json)
                                    .read("$.store.book[?(@.price > 10)]", List.class);
        print(authorsOfBooksWithISBN);
        print("****************Map****************");
        printListMap(expensiveBooks);
    }
    
    /**
     *读取json的一种写法
     *得到的值是一个String，所以不能用List存储 
     * */
    private static void getJsonValue3(String json) {
        //Will throw an java.lang.ClassCastException    
        //List<String> list = JsonPath.parse(json).read("$.store.book[0].author");
        //由于会抛异常，暂时注释上面一行，要用的话，应使用下面的格式
        
        //Works fine
        String author = JsonPath.parse(json).read("$.store.book[0].author");
        print(author);
    }
    
    /**
     *读取json的一种写法
     *支持逻辑表达式，&&和||  
     * */
    private static void getJsonValue4(String json) {
        List<Map<String, Object>> books1 =  JsonPath.parse(json)
                .read("$.store.book[?(@.price < 10 && @.category == 'fiction')]");
        List<Map<String, Object>> books2 =  JsonPath.parse(json)
                .read("$.store.book[?(@.category == 'reference' || @.price > 10)]");
        print("****************books1****************");
        printListMap(books1);
        print("****************books2****************");
        printListMap(books1);
    }
    
    private static void print(List<String> list) {
        for(Iterator<String> it = list.iterator();it.hasNext();) {
            System.out.println(it.next());
        }
    }
    
    private static void printOb(List<Object> list) {
        for(Iterator<Object> it = list.iterator();it.hasNext();) {
            print("****");
            System.out.println(it.next());
        }
    }
    
    private static void printListMap(List<Map<String, Object>> list) {
        for(Iterator<Map<String, Object>> it = list.iterator();it.hasNext();) {
            Map<String, Object> map = it.next();
            print("****");
            for(Iterator iterator =map.entrySet().iterator();iterator.hasNext();) {
                System.out.println(iterator.next());
            }
            
        }
    }
    
    private static void print(String s) {
        System.out.println(s);
    }
    
}