XML的两种解析方式逐行解析(SAX解析)节点解析(DOM解析);
SAX逐行解析
SAX：SimpleAPIfor XML。基于事件驱动的解析方式，逐行解析数据。（采用协议回调机制）
NSXMLParser是iOS自带的XML解析类。采用SAX方式解析数据
解析过程由NSXMLParserDelegate协议方法回调
解析过程：开始标签->取值->结束标签->取值
DOM解析
DOM：DocumentObjectModel（文档对象模型）。解析时需要将XML文件整体读入，并且将XML结构化成树状，使用时再通过树状结构读取相关数据
GDataXMLNode(这个类在下载包里面)是Google提供的开源XML解析类，对libxml2.dylib进行了Objective－C的封装
采用DOM方式解析数据
iOS中包含一个C语言的动态链接库libxml2.dylib，解析速度比NSXMLParser快
AppDelegate.m
#import "AppDelegate.h"
#import "MainViewController.h"
@implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
// Override point for customization after application launch.
self.window.backgroundColor = [UIColor whiteColor];
[self.window makeKeyAndVisible];
MainViewController *mainVC = [[MainViewController alloc] init];
UINavigationController *naviVC = [[UINavigationController alloc] initWithRootViewController:mainVC];
self.window.rootViewController = naviVC;
[naviVC release];
[mainVC release];
[_window release];
return YES;
}
- (void)dealloc
{
[_window release];
[super dealloc];
}
- (void)applicationWillResignActive:(UIApplication *)application
{
// Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
// Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}
- (void)applicationDidEnterBackground:(UIApplication *)application
{
// Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
// If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}
- (void)applicationWillEnterForeground:(UIApplication *)application
{
// Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
}
- (void)applicationDidBecomeActive:(UIApplication *)application
{
// Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}
- (void)applicationWillTerminate:(UIApplication *)application
{
// Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
}
@end
MainViewController.m
#import "MainViewController.h"
#import "XMLSAXParser.h"
#import "JSONParser.h"
@interface MainViewController ()
@end
@implementation MainViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
self.view.backgroundColor = [UIColor cyanColor];
//XML SAX解析(逐行解析)
XMLSAXParser *parser = [[XMLSAXParser alloc] init];
[parser startParse];
NSLog(@"解析后的%@",parser.array);
[parser release];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
/*
#pragma mark - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
// Get the new view controller using [segue destinationViewController].
// Pass the selected object to the new view controller.
}
*/
@end
XMLSAXParser.h #import <Foundation/Foundation.h> @interface XMLSAXParser : NSObject<NSXMLParserDelegate> @property (nonatomic , retain)NSMutableArray *array; //装学生对象 @property (nonatomic , retain)NSString *tempStr; //临时健在节点内容 - (void)startParse; //开始解析,逐行解析 - (void)startDOMParse; //开始dom解析,按节点解析 @end
XMLSAXParser.m
#import "XMLSAXParser.h"
#import "Student.h"
#import "GDataXMLNode.h"
@implementation XMLSAXParser
//XML解析:逐行解析
- (void)startParse;
{
//XML解析:逐行解析
//从文件列表中读取数据
//1.获取文件路径
NSString *sourcePath = [[NSBundle mainBundle] pathForResource:@"Student" ofType:@"xml"];
//2.通过路径把文件转换成NSData类型
NSData *data = [NSData dataWithContentsOfFile:sourcePath];
//创建的时候需要给parser一个字符串数据(NSData)
NSXMLParser *parser = [[NSXMLParser alloc] initWithData:data];
//设定代理人
parser.delegate = self;
//开始对文件进行解析
[parser parse];
//内存管理
[parser release];
}
- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{
//当找到节点头的时候,体统调用这个方法
NSLog(@"节点头");
if ([elementName isEqualToString:@"students"]) {
//当找到students节点头的时候,初始化数组
self.array = [NSMutableArray array];
}else if ([elementName isEqualToString:@"student"]){
//当找到student节点时候,创建一个新的学生对象,添加到数组中
Student *stu = [[Student alloc] init];
[self.array addObject:stu];
[stu release];
}
}
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
//当找到节点内容的时候,调用
NSLog(@"节点内容");
//把内容保存起来,只要碰到节点内容,下一个肯定是节点尾
self.tempStr = string;
}
- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{
//当找到节点尾时候调用
NSLog(@"节点尾");
//取得之前保存的student对象
Student *stu = [self.array lastObject]; //核心代码,懂了没 .........
if ([elementName isEqualToString:@"name"]) {
stu.name = self.tempStr;
}else if ([elementName isEqualToString:@"sex"]){
stu.sex = self.tempStr;
}else if ([elementName isEqualToString:@"phone"]){
stu.phone = self.tempStr;
}else if ([elementName isEqualToString:@"number"]){
stu.number = self.tempStr;
}
}
//开始dom解析,按节点解析
- (void)startDOMParse
{
//按节点解析
//1.获取要解析文件的文件信息
NSString *xmlPath = [[NSBundle mainBundle]pathForResource:@"Student" ofType:@"xml"];
NSData *data = [NSData dataWithContentsOfFile:xmlPath];
//参数1:要解析的xml串
//参数2:随便
//参数3:错误信息
GDataXMLDocument *doc = [[GDataXMLDocument alloc] initWithData:data options:0 error:nil];
//2.获取文件的根节点
GDataXMLElement *rootElement = [doc rootElement];
//3.进一步搜索所有的子节点
//返回一个装满了student节点(GDataXMLElement对象)的数组
NSArray *array = [rootElement elementsForName:@"student"];
self.array = [NSMutableArray array];
//4.遍历数组,把student节点的每个子节点取出来
for (GDataXMLElement *element in array) {
Student *stu = [[Student alloc] init];
GDataXMLElement *nameElement = [[element elementsForName:@"name"]lastObject];
//从name节点中取值
NSString *name = [nameElement stringValue];
//给学生对象的属性赋值
stu.name = name;
//把学生对象添加到数组中-----------其他的雷同
[self.array addObject:stu];
[stu release];
}
}
@end
Student.h #import <Foundation/Foundation.h> @interface Student : NSObject @property (nonatomic , retain)NSString *number; @property (nonatomic , retain)NSString *name; @property (nonatomic , retain)NSString *sex; @property (nonatomic , copy)NSString *phone; @end
Student.m
#import "Student.h"
@implementation Student
- (void)dealloc
{
[_name release];
[_number release];
[_sex release];
[_phone release];
[super dealloc];
}
//当这个类的对象被NSLog输出时候,系统会先调用这个方法,如果这个方法被重写,就直接输出重写的内容,否则就输出系统默认的内容
- (NSString *)description
{
return [NSString stringWithFormat:@"name:%@ sex:%@ phone:%@ number:%@", self.name, self.sex, self.phone, self.number];
}
@end
这里需要注意的是添加第三方类的步骤:
直接添加第三方类是有错的
在GDataXMLNode.h中
// libxml includes require that the target Header Search Paths contain
//
// /usr/include/libxml2
//
// and Other Linker Flags contain
//
// -lxml2
在下面的对上面的文件中首先搜索Header Search 然后在第二行中添加上/usr/include/libxml2
然后同理搜索Other Linker然后在第二行中添加上-lxml2
这样第三方类就可以使用了 .
XML在不同的语言里解析方式都是一样的,只不过实现的语法不同而已。基本的解析方式有两种,一种叫SAX，另一种叫DOM。SAX是基于事件流的解析,DOM是基于XML文档树结构的解析.假设我们XML的内容和结构如下:
[xhtml] view plaincopy
<?xml version="1.0" encoding="UTF-8"?> <employees> <employee> <name>ddviplinux</name> <sex>m</sex> <age>30</age> </employee> </employees>
下面是解析XMl常用的Dom和Sex方法：
1.DOM生成和解析XML文档
为 XML 文档的已解析版本定义了一组接口。解析器读入整个文档，然后构建一个驻留内存的树结构，然后代码就可以使用 DOM 接口来操作这个树结构。优点：整个文档树在内存中，便于操作；支持删除、修改、重新排列等多种功能；缺点：将整个文档调入内存（包括无用的节点），浪费时间和空间；使用场合：一旦解析了文档还需多次访问这些数据；硬件资源充足（内存、CPU）。
[java] view plaincopy
public void parserXml(String fileName) {
try {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document document = db.parse(fileName);
NodeList employees = document.getChildNodes();
for (int i = 0; i < employees.getLength(); i++) {
Node employee = employees.item(i);
NodeList employeeInfo = employee.getChildNodes();
for (int j = 0; j < employeeInfo.getLength(); j++) {
Node node = employeeInfo.item(j);
NodeList employeeMeta = node.getChildNodes();
for (int k = 0; k < employeeMeta.getLength(); k++) {
System.out.println(employeeMeta.item(k).getNodeName() + ":" + employeeMeta.item(k).getTextContent());
}
}
}
System.out.println("解析完毕");
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
2.SAX生成和解析XML文档
为解决DOM的问题，出现了SAX。SAX ，事件驱动。当解析器发现元素开始、元素结束、文本、文档的开始或结束等时，发送事件，程序员编写响应这些事件的代码，保存数据。优点：不用事先调入整个文档，占用资源少；SAX解析器代码比DOM解析器代码小，适于Applet，下载。缺点：不是持久的；事件过后，若没保存数据，那么数据就丢了；无状态性；从事件中只能得到文本，但不知该文本属于哪个元素；使用场合：Applet;只需XML文档的少量内容，很少回头访问；机器内存少；
[java] view plaincopy
public void parserXml(String fileName) {
SAXParserFactory saxfac = SAXParserFactory.newInstance();
try {
SAXParser saxparser = saxfac.newSAXParser();
InputStream is = new FileInputStream(fileName);
saxparser.parse(is, new MySAXHandler());
} catch (Exception e) {
e.printStackTrace();
}
}