iOS_XML与JSON解析

XML与JSON简介
XML

可扩展标记语言

用于标记电子文件使其具有结构性的标记语言，可以用来标记数据、定义数据类型，是一种允许用户对自己的标记语言进行定义的源语言

易读性高，编码手写难度小，数据量大

NSXMLParser解析方法
我们所用到的NSXMLParser是采用SAX方法解析
SAX（Simple API for XML）

只能读，不能修改，只能顺序访问，适合解析大型XML，解析速度快

常应用于处理大量数据的XML，实现异构系统的数据访问，实现跨平台

从文档的开始通过每一节点移动，定位一个特定的节点

DOM（Document Object Model）

不仅能读，还能修改，而且能够实现随机访问，缺点是解析速度慢，适合解析小型文档

一般应用与小型的配置XML，方便操作

为载入到内存的文档节点建立类型描述，呈现可横向移动、潜在巨大的树型结构

在内存中生成节点树操作代价昂贵

xmlParser解析过程
NSXMLParser解析过程
1.创建NSXMLParser实例，并传入从服务器接收的XML数据
2.定义解析器代理
3.解析器解析
4.通过解析代理方法完成XML数据的解析

使用XML解析文档时使用协议<NSXMLParserDelegate>，实现它的代理方法

// 1. 开始解析某个元素，会遍历整个XML，识别元素节点名称

- (void)parser:didStartElement:namespaceURI:qualifiedName:attributes:

// 2. 文本节点，得到文本节点里存储的信息数据，对于大数据可能会接收多次！为了节约内存开销

- (void)parser:foundCharacters:

// 3. 结束某个节点，存储从parser:foundCharacters:方法中获取到的信息

- (void)parser:didEndElement:namespaceURI:qualifiedName:

注意：在解析过程中，上述三个方法会不停的重复执行，直到遍历完成为止

// 4. 开始解析XML文档

- (void)parserDidStartDocument:

// 5. 解析XML文档结束

- (void)parserDidEndDocument:

// 6. 解析出错

- (void)parser:parseErrorOccurred:

接下来通过案例来详细分析XML的解析

#import "ViewController.h"
#import "Student.h"
@interface ViewController ()<NSXMLParserDelegate>
//student数组
@property(strong,nonatomic)NSMutableArray *students;
@property(strong,nonatomic)Student *currentStudent;
//当前的元素名
@property(strong,nonatomic)NSString *elementName;
//元素值
@property(strong,nonatomic)NSMutableString *elementValue;
@end

@implementation ViewController
//XMLParse解析过程
-(void)XMLParse
{
//1.从网络上获取xml文件数据
NSData *xmlData = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://127.0.0.1/userManager/student.xml"]];
//2.创建XML解析对象
NSXMLParser *parser = [[NSXMLParser alloc]initWithData:xmlData];
//3.设置代理
parser.delegate = self;
//4.开始解析
[parser parse];
}
- (void)viewDidLoad {
[super viewDidLoad];
//调用解析方法
[self XMLParse];
}
#pragma mark - NSXMLParser代理方法
//开始解析，解析的准备工作
-(void)parserDidStartDocument:(NSXMLParser *)parser
{
self.students = [NSMutableArray array];
}
//解析XML结束，输出文档的内容
-(void)parserDidEndDocument:(NSXMLParser *)parser
{
NSLog(@"%@",self.students);
}
//开始解析某个元素，会遍历整个XML，识别元素结点名称
-(void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{
if ([elementName isEqualToString:@"student"])
{
//创建新的对象
self.currentStudent = [[Student alloc]init];
}
else if([elementName isEqualToString:@"name"]||
[elementName isEqualToString:@"age"]||
[elementName isEqualToString:@"sex"])
{
self.elementValue = [[NSMutableString alloc]init];
}
}
//文本节点，得到文本节点里存储的信息数据，对于大数据可能会接收多次，
-(void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
//将找到的字符，跟已取的字符进行拼接
[self.elementValue appendString:string];
}
//结束某个节点，存储获取到的信息
-(void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{
if ([elementName isEqualToString:@"name"])
{
//将读取到的元素值，赋值给对应的属性名
self.currentStudent.name = self.elementValue;
}
else if ([elementName isEqualToString:@"age"])
{
self.currentStudent.age = [self.elementValue integerValue];
}
else if([elementName isEqualToString:@"sex"])
{
self.currentStudent.sex = [self.elementValue characterAtIndex:0];
}
else if ([elementName isEqualToString:@"student"])
{
if (self.currentStudent)
{
[self.students addObject:self.currentStudent];
}
}
}
//差错解析
-(void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError
{
NSLog(@"Error reason:%@",parseError);
}
@end

下面这个案例就是实现citier.xml的解析

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>provinces</key>
<array>
<string>安徽</string>
<string>澳门</string>
<string>北京</string>
<string>重庆</string>
<string>福建</string>
<string>甘肃</string>
<string>广东</string>
<string>广西</string>
<string>贵州</string>
<string>海南</string>
<string>河北</string>
<string>河南</string>
<string>黑龙江</string>
<string>湖北</string>
<string>湖南</string>
<string>吉林</string>
<string>江苏</string>
<string>江西</string>
<string>辽宁</string>
<string>内蒙古</string>
<string>宁夏</string>
<string>青海</string>
<string>山东</string>
<string>山西</string>
<string>陕西</string>
<string>上海</string>
<string>四川</string>
<string>台湾</string>
<string>天津</string>
<string>西藏</string>
<string>香港</string>
<string>新疆</string>
<string>云南</string>
<string>浙江</string>
</array>
<key>cities</key>
<dict>
<key>北京</key>
<array>
<string>东城区</string>
<string>西城区</string>
<string>崇文区</string>
<string>宣武区</string>
<string>海淀区</string>
<string>朝阳区</string>
<string>丰台区</string>
<string>石景山区</string>
<string>通州区</string>
<string>顺义区</string>
<string>房山区</string>
<string>大兴区</string>
<string>昌平区</string>
<string>怀柔区</string>
<string>平谷区</string>
<string>门头沟区</string>
<string>密云县</string>
<string>延庆县</string>
</array>
<key>重庆</key>
<array>
<string>重庆</string>
</array>
<key>上海</key>
<array>
<string>上海</string>
</array>
<key>天津</key>
<array>
<string>天津</string>
</array>
<key>安徽</key>
<array>
<string>合肥</string>
<string>安庆</string>
<string>蚌埠</string>
<string>亳州</string>
<string>巢湖</string>
<string>池州</string>
<string>滁州</string>
<string>阜阳</string>
<string>淮北</string>
<string>淮南</string>
<string>黄山</string>
<string>黄山景区</string>
<string>九华山景区</string>
<string>六安</string>
<string>马鞍山</string>
<string>青阳</string>
<string>宿州</string>
<string>铜陵</string>
<string>芜湖</string>
<string>宣城</string>
</array>
<key>福建</key>
<array>
<string>福州</string>
<string>龙岩</string>
<string>南平</string>
<string>宁德</string>
<string>莆田</string>
<string>泉州</string>
<string>三明</string>
<string>厦门</string>
<string>永安</string>
<string>漳州</string>
</array>
<key>广东</key>
<array>
<string>广州</string>
<string>潮州</string>
<string>从化</string>
<string>东莞</string>
<string>佛山</string>
<string>河源</string>
<string>鹤山</string>
<string>化州</string>
<string>惠州</string>
<string>江门</string>
<string>揭阳</string>
<string>茂名</string>
<string>梅州</string>
<string>清远</string>
<string>汕头</string>
<string>汕尾</string>
<string>韶关</string>
<string>深圳</string>
<string>阳江</string>
<string>云浮</string>
<string>湛江</string>
<string>肇庆</string>
<string>中山</string>
<string>珠海</string>
</array>
<key>甘肃</key>
<array>
<string>兰州</string>
<string>白银</string>
<string>定西</string>
<string>甘南</string>
<string>嘉峪关</string>
<string>酒泉</string>
<string>临夏</string>
<string>陇南</string>
<string>平凉</string>
<string>庆阳</string>
<string>天水</string>
<string>武威</string>
<string>张掖</string>
</array>
<key>广西</key>
<array>
<string>南宁</string>
<string>百色</string>
<string>北海</string>
<string>北流</string>
<string>崇左</string>
<string>防城港</string>
<string>贵港</string>
<string>桂林</string>
<string>桂平</string>
<string>河池</string>
<string>贺州</string>
<string>来宾</string>
<string>柳州</string>
<string>钦州</string>
<string>梧州</string>
<string>宜州</string>
<string>玉林</string>
</array>
<key>贵州</key>
<array>
<string>贵阳</string>
<string>安顺</string>
<string>毕节</string>
<string>都匀</string>
<string>凯里</string>
<string>六盘水</string>
<string>铜仁</string>
<string>兴义</string>
<string>遵义</string>
</array>
<key>河北</key>
<array>
<string>石家庄</string>
<string>保定</string>
<string>泊头</string>
<string>沧州</string>
<string>承德</string>
<string>邯郸</string>
<string>河间</string>
<string>衡水</string>
<string>廊坊</string>
<string>秦皇岛</string>
<string>任丘</string>
<string>唐山</string>
<string>邢台</string>
<string>张家口</string>
</array>
<key>河南</key>
<array>
<string>郑州</string>
<string>安阳</string>
<string>鹤壁</string>
<string>济源</string>
<string>焦作</string>
<string>开封</string>
<string>洛阳</string>
<string>漯河</string>
<string>南阳</string>
<string>平顶山</string>
<string>濮阳</string>
<string>三门峡</string>
<string>商丘</string>
<string>新乡</string>
<string>信阳</string>
<string>许昌</string>
<string>周口</string>
<string>驻马店</string>
</array>
<key>黑龙江</key>
<array>
<string>哈尔滨</string>
<string>大庆</string>
<string>大兴安岭</string>
<string>鹤岗</string>
<string>黑河</string>
<string>虎林</string>
<string>鸡西</string>
<string>佳木斯</string>
<string>密山</string>
<string>牡丹江</string>
<string>宁安</string>
<string>七台河</string>
<string>齐齐哈尔</string>
<string>双鸭山</string>
<string>绥化</string>
<string>五常</string>
<string>伊春</string>
</array>
<key>湖北</key>
<array>
<string>武汉</string>
<string>鄂州</string>
<string>恩施</string>
<string>黄冈</string>
<string>黄石</string>
<string>荆门</string>
<string>荆州</string>
<string>潜江</string>
<string>十堰</string>
<string>随州</string>
<string>天门</string>
<string>仙桃</string>
<string>咸宁</string>
<string>襄樊</string>
<string>孝感</string>
<string>宜昌</string>
</array>
<key>湖南</key>
<array>
<string>长沙</string>
<string>常德</string>
<string>郴州</string>
<string>衡阳</string>
<string>怀化</string>
<string>吉首</string>
<string>耒阳</string>
<string>冷水江</string>
<string>娄底</string>
<string>韶山</string>
<string>邵阳</string>
<string>湘潭</string>
<string>湘乡</string>
<string>益阳</string>
<string>永州</string>
<string>岳阳</string>
<string>张家界</string>
<string>株州</string>
</array>
<key>吉林</key>
<array>
<string>长春</string>
<string>白城</string>
<string>白山</string>
<string>珲春</string>
<string>吉林</string>
<string>辽源</string>
<string>龙井</string>
<string>舒兰</string>
<string>四平</string>
<string>松原</string>
<string>通化</string>
<string>延边</string>
</array>
<key>江苏</key>
<array>
<string>南京</string>
<string>常州</string>
<string>高邮</string>
<string>淮安</string>
<string>连云港</string>
<string>南通</string>
<string>苏州</string>
<string>宿迁</string>
<string>太仓</string>
<string>泰州</string>
<string>无锡</string>
<string>新沂</string>
<string>徐州</string>
<string>盐城</string>
<string>扬州</string>
<string>镇江</string>
</array>
<key>江西</key>
<array>
<string>南昌</string>
<string>抚州</string>
<string>赣州</string>
<string>吉安</string>
<string>景德镇</string>
<string>九江</string>
<string>萍乡</string>
<string>上饶</string>
<string>新余</string>
<string>宜春</string>
<string>鹰潭</string>
</array>
<key>辽宁</key>
<array>
<string>沈阳</string>
<string>鞍山</string>
<string>本溪</string>
<string>朝阳</string>
<string>大连</string>
<string>丹东</string>
<string>抚顺</string>
<string>阜新</string>
<string>葫芦岛</string>
<string>锦州</string>
<string>辽阳</string>
<string>盘锦</string>
<string>铁岭</string>
<string>营口</string>
</array>
<key>内蒙古</key>
<array>
<string>呼和浩特</string>
<string>阿拉善盟</string>
<string>巴彦淖尔盟</string>
<string>包头</string>
<string>赤峰</string>
<string>鄂尔多斯</string>
<string>呼伦贝尔</string>
<string>通辽</string>
<string>乌海</string>
<string>乌兰察布盟</string>
<string>锡林郭勒盟</string>
<string>兴安盟</string>
</array>
<key>宁夏</key>
<array>
<string>银川</string>
<string>固原</string>
<string>石嘴山</string>
<string>吴忠</string>
<string>中卫</string>
</array>
<key>青海</key>
<array>
<string>西宁</string>
<string>果洛</string>
<string>海北</string>
<string>海东</string>
<string>海南</string>
<string>海西</string>
<string>黄南</string>
<string>玉树</string>
</array>
<key>四川</key>
<array>
<string>成都</string>
<string>阿坝</string>
<string>巴中</string>
<string>崇州</string>
<string>达州</string>
<string>大邑</string>
<string>德阳</string>
<string>都江堰</string>
<string>峨眉山</string>
<string>甘孜</string>
<string>广安</string>
<string>广元</string>
<string>江油</string>
<string>金堂</string>
<string>乐山</string>
<string>泸州</string>
<string>眉山</string>
<string>绵阳</string>
<string>内江</string>
<string>南充</string>
<string>攀枝花</string>
<string>遂宁</string>
<string>西昌</string>
<string>雅安</string>
<string>宜宾</string>
<string>资阳</string>
<string>自贡</string>
</array>
<key>山东</key>
<array>
<string>济南</string>
<string>滨州</string>
<string>德州</string>
<string>东营</string>
<string>肥城</string>
<string>海阳</string>
<string>菏泽</string>
<string>济宁</string>
<string>莱芜</string>
<string>莱阳</string>
<string>聊城</string>
<string>临沂</string>
<string>平度</string>
<string>青岛</string>
<string>青州</string>
<string>日照</string>
<string>泰安</string>
<string>威海</string>
<string>潍坊</string>
<string>烟台</string>
<string>枣庄</string>
<string>章丘</string>
<string>淄博</string>
</array>
<key>陕西</key>
<array>
<string>西安</string>
<string>安康</string>
<string>宝鸡</string>
<string>汉中</string>
<string>商洛</string>
<string>铜川</string>
<string>渭南</string>
<string>咸阳</string>
<string>兴平</string>
<string>延安</string>
<string>榆林</string>
</array>
<key>山西</key>
<array>
<string>太原</string>
<string>长治</string>
<string>大同</string>
<string>晋城</string>
<string>晋中</string>
<string>临汾</string>
<string>吕梁</string>
<string>朔州</string>
<string>忻州</string>
<string>阳泉</string>
<string>运城</string>
</array>
<key>新疆</key>
<array>
<string>乌鲁木齐</string>
<string>阿克苏</string>
<string>阿拉尔</string>
<string>阿图什</string>
<string>博乐</string>
<string>昌吉</string>
<string>哈密</string>
<string>和田</string>
<string>喀什</string>
<string>克拉玛依</string>
<string>库尔勒</string>
<string>石河子</string>
<string>图木舒克</string>
<string>吐鲁番</string>
<string>五家渠</string>
<string>伊宁</string>
</array>
<key>西藏</key>
<array>
<string>拉萨</string>
<string>阿里</string>
<string>昌都</string>
<string>林芝</string>
<string>那曲</string>
<string>日喀则</string>
<string>山南</string>
</array>
<key>云南</key>
<array>
<string>昆明</string>
<string>保山</string>
<string>楚雄</string>
<string>大理</string>
<string>德宏</string>
<string>迪庆</string>
<string>个旧</string>
<string>丽江</string>
<string>临沧</string>
<string>怒江</string>
<string>曲靖</string>
<string>思茅</string>
<string>文山</string>
<string>西双版纳</string>
<string>玉溪</string>
<string>昭通</string>
</array>
<key>浙江</key>
<array>
<string>杭州</string>
<string>北仑</string>
<string>慈溪</string>
<string>奉化</string>
<string>湖州</string>
<string>嘉兴</string>
<string>金华</string>
<string>丽水</string>
<string>临海</string>
<string>宁波</string>
<string>宁海</string>
<string>衢州</string>
<string>三门</string>
<string>绍兴</string>
<string>台州</string>
<string>天台</string>
<string>温岭</string>
<string>温州</string>
<string>仙居</string>
<string>象山</string>
<string>义乌</string>
<string>余姚</string>
<string>舟山</string>
</array>
<key>澳门</key>
<array>
<string>澳门</string>
</array>
<key>台湾</key>
<array>
<string>台北</string>
<string>高雄</string>
<string>台南</string>
<string>台中</string>
</array>
<key>香港</key>
<array>
<string>香港</string>
</array>
<key>海南</key>
<array>
<string>海口</string>
<string>儋州</string>
<string>东方</string>
<string>琼海</string>
<string>三亚</string>
<string>万宁</string>
<string>文昌</string>
<string>五指山</string>
</array>
</dict>
</dict>
</plist>

cities.xml
实现代码如下：

#import "ViewController.h"

@interface ViewController ()<NSXMLParserDelegate>
@property(strong,nonatomic)NSMutableDictionary *dic;
@property(strong,nonatomic)NSMutableArray *array;
@property(strong,nonatomic)NSMutableDictionary *cities;
@property(strong,nonatomic)NSString *keyName;
@property(strong,nonatomic)NSMutableString *elementValue;

@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];
[self XMLParser];
}

-(void)XMLParser
{
//1.获取网络数据
NSData *xmlData = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://127.0.0.1/userManager/cities.xml"]];
//2.创建解析对象
NSXMLParser *parser = [[NSXMLParser alloc]initWithData:xmlData];
//3.设置代理
parser.delegate = self;
//4.开始解析
[parser parse];
}
#pragma mark - NSXMLParser代理方法
//文档开始
-(void)parserDidStartDocument:(NSXMLParser *)parser
{
self.dic = [NSMutableDictionary dictionary];
}
//文档结束
-(void)parserDidEndDocument:(NSXMLParser *)parser
{
[self.dic setObject:self.cities forKey:@"cities"];
NSLog(@"%@",self.dic);
}
//元素开始
-(void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{
if ([elementName isEqualToString:@"array"])
{
self.array = [NSMutableArray array];
}
else if ([elementName isEqualToString:@"dict"])
{
if ([self.keyName hasPrefix:@"cities"])
{
self.cities = [NSMutableDictionary dictionary];
}
}
else if ([elementName isEqualToString:@"string"]||
[elementName isEqualToString:@"key"])
{
self.elementValue = [[NSMutableString alloc]init];
}
}
//元素结束
-(void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{
if ([elementName isEqualToString:@"array"])
{
if ([self.keyName hasPrefix:@"provinces"])
{
[self.dic setObject:self.array forKey:self.keyName];
}
else
{
[self.cities setObject:self.array forKey:self.keyName];
}
}
else if ([elementName isEqualToString:@"key"])
{
self.keyName = self.elementValue;
}
else if ([elementName isEqualToString:@"string"])
{
[self.array addObject:self.elementValue];
}

}
//找字符
-(void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
[self.elementValue appendString:string];
}
//出错解析
-(void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError
{
NSLog(@"error reason:%@",parseError);
}
@end

JSON

作为一种轻量级的数据交换格式，正在逐步取代XML，成为网络数据的通用格式

基于JavaScript的一个子集

易读性略差，编码手写难度大，数据量小

JSON格式取代了XML给网络传输带来了很大的便利，但是却没有了XML的一目了然，尤其是JSON数据很长的时候，我们会陷入繁琐复杂的数据节点查找中

作为一种轻量级的数据交换格式，JSON正在逐步取代XML，成为网络数据的通用格式。废话不多说，直接上代码。

案例1:使用NSDictionary创建JSON文件

-(void)dataFromJSONObject
{
//从网络数据生成字典
NSDictionary *dic = [NSDictionary dictionaryWithContentsOfURL:[NSURL URLWithString:@"http://127.0.0.1/userManager/cities.xml"]];
NSError *error = nil;
//将字典转换成JSON数据
//    NSJSONWritingPrettyPrinted：的意思是将生成的json数据格式化输出，这样可读性高，不设置则输出的json字符串就是一整行。
NSData *data = [NSJSONSerialization dataWithJSONObject:dic options:NSJSONWritingPrettyPrinted error:&error];
if (!error)
{
//拼接路径
NSString *document = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
NSLog(@"%@",document);
NSString *jsonPath = [document stringByAppendingPathComponent:@"cities.json"];
//将数据写入文件中
[[NSFileManager defaultManager]createFileAtPath:jsonPath contents:data attributes:nil];
}
}

案例2：读取已有的JSON文件内容

-(void)JSONObjectFromData
{
NSURL *url = [NSURL URLWithString:@"http://127.0.0.1/userManager/cities.json"];
NSData *data = [NSData dataWithContentsOfURL:url];
NSError *error = nil;
//读取文件内容
id obj = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];
if (!error)
{
//判断对象的类型
if ([obj isKindOfClass:[NSDictionary class]])
{
NSDictionary *dic = obj;
NSLog(@"dic");
NSArray *provinces = [dic objectForKey:@"provinces"];
[provinces enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop)
{
NSLog(@"%@",obj);
}];
}
else if ([obj isKindOfClass:[NSArray class]])
{
NSArray *array = obj;
NSLog(@"array");
}
}
}