jsoncpp库使用例子

太过爱你忘了你带给我的痛 2022-07-15 14:40 170阅读 0赞

**从json格式的字符串中解析读：**

//g++ jsoncpp_read_sample.cpp -I/usr/local/include/jsoncpp -ljsoncpp
    
    #include <iostream>  
    #include <string>  
    #include <json/json.h>
    
    
    int main(void)  
    {  
    	std::string strjson = "{\"key1\":\"value1\",\"array\":[{\"key2\":\"value2\"},{\"key2\":\"value3\"},{\"key2\":\"value4\"}]}";
    /*
    {	
    	"key1":"value1",
    	"array":
    	[
    		{"key2":"value2"},
    		{"key2":"value3"},
    		{"key2":"value4"}
    	]
    }
    */  
    	Json::Reader reader;  
    	Json::Value root;  
    	
    	if (reader.parse(strjson, root))  
    	{  
    		std::string out = root["key1"].asString();  
    		std::cout << out << std::endl;  
    		const Json::Value arrayObj = root["array"];  
    		for (int i=0; i<arrayObj.size(); i++)  
    		{  
    			out = arrayObj[i]["key2"].asString();  
    			std::cout << out << std::endl;  
    		}
    	}
    	
    	return 0;  
    }

**将json对象的值输出：**

//g++ jsoncpp_write_sample.cpp -I/usr/local/include/jsoncpp -ljsoncpp
    
    #include <iostream>  
    #include <string>  
    #include <json/json.h>
    
    
    int main(void)  
    {
    	Json::Value root;  
    	Json::Value arrayObj;  
    	Json::Value item;  
    	
    	for (int i = 0; i < 10; i ++)  
    	{  
    		item["key"] = i;  
    		arrayObj.append(item);  
    	}  
    	
    	root["key1"] = "value1";  
    	root["key2"] = "value2";  
    	root["array"] = arrayObj;  
    	//root.toStyledString();  
    	//格式化输出Json格式内容
    	std::string out = root.toStyledString();  
    	std::cout << out << std::endl;  
    	std::cout << "--------------------" << std::endl;
    	
    	//未格式化输出Json格式内容
    	Json::FastWriter writer;
    	std::string json_str = writer.write(root);
    	std::cout << json_str << std::endl;  
    	return 0;  
    }

从json格式的文件中解析读：

文件内容为

{ 
    	"mmac": "e4:95:6e:4e:ed:6e", 
    	"wmac": "ff:ff:ff:ff:ff:ff", 
    	"data": 
    	[ 	{ "mac": "3c:46:d8:19:6a:e3", "rssi": "-82", "tmc": "ff:ff:ff:ff:ff:ff"	}, 
    		{ "mac": "90:18:7c:f2:45:cc", "rssi": "-71", "tmc": "ff:ff:ff:ff:ff:ff" }, 
    		{ "mac": "b8:44:d9:02:b0:94", "rssi": "-86", "tmc": "ff:ff:ff:ff:ff:ff" }, 
    		{ "mac": "dc:85:de:6a:f8:37", "rssi": "-44", "tmc": "ff:ff:ff:ff:ff:ff" }, 
    		{ "mac": "ec:0e:c4:60:b7:95", "rssi": "-77", "tmc": "ff:ff:ff:ff:ff:ff" } 
    	] 
    }

//g++ read_json_file.cpp -I/usr/local/include/jsoncpp -ljsoncpp
    
    #include <fstream>
    #include <iostream>  
    #include <string>  
    #include <cassert>
    #include <json/json.h>
    
    int main(void)  
    {  
    	std::ifstream ifs;
    	
    	ifs.open("test.json");
    	
    	assert(ifs.is_open());
    	
    	Json::Reader reader;
    	Json::Value root;
    	
    	if (!reader.parse(ifs, root, false))
    	{
    		std::cout<<"reader.parse() fail"<<std::endl;
    		return -1;
    	}
    	
    	std::string out = root["mmac"].asString();  
    	std::cout << "mmac  " << out << std::endl; 
    	out = root["wmac"].asString();  
    	std::cout << "wmac  " << out << std::endl; 
    		
    	const Json::Value arrayObj = root["data"]; 
    	for (int i=0; i<arrayObj.size(); i++)  
    	{  
    		out = arrayObj[i]["mac"].asString();  
    		std::cout << "data-->mac  " << out << std::endl;  
    			
    		out = arrayObj[i]["rssi"].asString();  
    		std::cout << "data-->rssi  " << out << std::endl; 
    
    		out = arrayObj[i]["tmc"].asString();  
    		std::cout << "data-->tmc  " << out << std::endl; 
    		
    	}
    	
    	return 0; 
    }