使用jsonpath解析json内容

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 authors1 = JsonPath.read(json, "$.store.book[*].author");
        
        //All authors：获取所有json中所有author的值
        List 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