JAVA嵌套解析Json字符串 - 递归方法

1、需求

后台接口测试中，http request的response中data是json结构，数据较复杂，嵌套多层，类似于：

{
	key1 : value1,
	key2 : value2,
	.............
	keyT: [
	      {
   		key11: value11,
   		key12: value12,
   		......
   		keyA:   value1A,
   		......
     		keyB:   value1B,
   		.......
   		keyN: value1N
	       },
	       {
   		key11: value21,
   		key12: value22,
   		......
   		keyA:   value2A,
   		......
     		keyB:   value2B,
   		.......
   		keyN: value2N
	       },
	.........
	keyM: valueM,
}

目的：希望从层层嵌套的json串中，将里面的json数组中多组keyA，keyB对应的value抓取到，并成组配对打印到文件中。类似于：

keyA:value1A     keyB:value1B
keyA:value2A     keyB:value2B
..........
keyA:valueKA     keyB:valueKB

2、解题思路

网上Google了一把这类json嵌套解析的方法，有些源码实现较复杂，有些只是提供个思路，都不是很好。算了，自己来写吧。

最笨的方法是想抓什么数据，直接检索(类似于linux的grep的思路），但这种方式扩展性差，并且在json串较复杂时(如部分为空)，检索结果容易有偏差。

为减少代码量，考虑用 递归思路来做。

代码如下：

package testJa;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.util.Iterator;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

//this class to analysis json via recursion
public class jsonOp {
	public void jsonPattern(String inFile,String outFile,String patt) throws IOException, JSONException{
		File fi = new File(inFile);
		if(fi.isFile() && fi.exists()){
			//read file
			InputStreamReader in = new InputStreamReader(new FileInputStream(fi));
			BufferedReader br = new BufferedReader(in);
			String jsonStr = br.readLine(); //read by line
			//write file
			File fo = new File(outFile);
			OutputStream out = new FileOutputStream(fo);
			
			String [] pats = patt.split(":");
			String [] pat_detail = pats[1].split(",");
			JSONArray ja = getJsonArray(jsonStr,pats[0]); //get target json array
			
			//get target items from json array via pattern
			int len = ja.length();
			for(int i=0;i


代码解读：

1. main中给出了个实例，其中“patt”中存放要匹配的串，seats是jsonArray对应的key，seatID，seatName是jsonArray中的每个json体中抽取的key

String patt = "seats:seatID,seatName";

2. 为简单期间，输入和输出都从文件中读取，有需要的可以把输入文件砍掉，直接读入是个String即可

String inFile = "/Users/xx/Downloads/tmp/seatidseatname.txt";
String outFile= "/Users/xx/Downloads/tmp/out.txt";

其中输入文件中的值为：(飘红部分是要抓取的部分)

{"code":"0000","message”:”xx”,”data":{"scheduleID”:xx,”cinemaID”:”xx”,”showID”:”xx”,”currentTime”:xx,”hallName":"4","cinemaName”:”xx”,"openTime":"22:45:00","openDate":"2017-09-14","loverSeat":false,"mobile”:”xx”,"regular":false,"seats":[{"status":1,"seatID":"3661","topPx":42,"leftPx":175,"flag":0,"rowName":"A","seatName":"A01","column":0,"row":0},{"status":1,"seatID":"3662","topPx":42,"leftPx":208,"flag":0,"rowName":"A","seatName":"A02","column":0,"row":0},{"status":1,"seatID":"3787","topPx":386,"leftPx":505,"flag":0,"rowName":"L","seatName":"L11","column":0,"row":0},{"status":0,"seatID":"3788","topPx":386,"leftPx":538,"flag":0,"rowName":"L","seatName":"L12","column":0,"row":0}],"soldCount":21,"minTopPx":42,"maxLeftPx":538,"maxTopPx":386,"maxColumn":0,"minColumn":0,"maxRow":0,"minRow":0}}}

3、getJsonArray函数是递归函数

要注意，递归函数的特点，获取目标值后需从递归函数（层层堆栈结构）中退出，所以在递归函数的调用后需要有判断进行退出：

						JSONArray ja = getJsonArray(value,listKey); //recursion
						if(ja!=null){
							return ja;
						}

如果没有这个条件判断，返回值是有问题的。

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