标题中的Get和Post是请求的两种方式，同步和异步属于实现的方法，Get方式有同步和异步两种方法，Post同理也有两种。稍微有点Web知识的，对Get和Post应该不会陌生，常说的请求处理响应，基本上请求的是都是这两个哥们，Http最开始定义的与服务器交互的方式有八种，不过随着时间的进化，现在基本上使用的只剩下这两种，有兴趣的可以参考本人之前的博客Http协议中Get和Post的浅谈，iOS客户端需要和服务端打交道，Get和Post是跑不了的，本文中包含iOS代码和少量Java服务端代码，开始正题吧.
Get和Post同步请求
Get和Post同步请求的时候最常见的是登录，输入各种密码才能看到的功能，必须是同步，异步在Web上局部刷新的时候用的比较多，比较耗时的时候执行异步请求，可以让客户先看到一部分功能，然后慢慢刷新，举个例子就是餐馆吃饭的时候点了十几个菜，给你先上一两个吃着，之后给别人上，剩下的慢慢上。大概就是这样的。弄了几个按钮先上图:
先贴下同步请求的代码:
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//设置URL路径
NSString
*urlStr=[
NSString
stringWithFormat:@
"http://localhost:8080/MyWeb/Book?username=%@&password=%@&type=get"
,@
"博客园"
,@
"keso"
];
urlStr=[urlStr stringByAddingPercentEscapesUsingEncoding:
NSUTF8StringEncoding
];
NSURL
*url=[
NSURL
URLWithString:urlStr];
//通过URL设置网络请求
NSURLRequest
*request = [[
NSURLRequest
alloc]initWithURL:url cachePolicy:
NSURLRequestUseProtocolCachePolicy
timeoutInterval:10];
NSError
*error=
nil
;
//获取服务器数据
NSData
*requestData= [
NSURLConnection
sendSynchronousRequest:request returningResponse:
nil
error:&error];
if
(error) {
NSLog
(@
"错误信息:%@"
,[error localizedDescription]);
}
else
{
NSString
*result=[[
NSString
alloc]initWithData:requestData encoding:
NSUTF8StringEncoding
];
NSLog
(@
"返回结果:%@"
,result);
}
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代码很多，需要解释一下:
①URL如果有中文无法传递，需要编码一下:
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[urlStr stringByAddingPercentEscapesUsingEncoding:
NSUTF8StringEncoding
];
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②设置网路请求中的代码，有两个参数，最后一个设置请求的时间，这个不用说什么，重点说下缓存策略cachePolicy，系统中的定义如下:
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typedef
NS_ENUM
(
NSUInteger
,
NSURLRequestCachePolicy
)
{
NSURLRequestUseProtocolCachePolicy
= 0,
NSURLRequestReloadIgnoringLocalCacheData
= 1,
NSURLRequestReloadIgnoringLocalAndRemoteCacheData
= 4,
// Unimplemented
NSURLRequestReloadIgnoringCacheData
=
NSURLRequestReloadIgnoringLocalCacheData
,
NSURLRequestReturnCacheDataElseLoad
= 2,
NSURLRequestReturnCacheDataDontLoad
= 3,
NSURLRequestReloadRevalidatingCacheData
= 5,
// Unimplemented
};
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NSURLRequestUseProtocolCachePolicy（基础策略）,NSURLRequestReloadIgnoringLocalCacheData（忽略本地缓存）;
NSURLRequestReloadIgnoringLocalAndRemoteCacheData（无视任何缓存策略，无论是本地的还是远程的，总是从原地址重新下载）;
NSURLRequestReturnCacheDataElseLoad（首先使用缓存，如果没有本地缓存，才从原地址下载);
NSURLRequestReturnCacheDataDontLoad（使用本地缓存，从不下载，如果本地没有缓存，则请求失败，此策略多用于离线操作）;
NSURLRequestReloadRevalidatingCacheData（如果本地缓存是有效的则不下载，其他任何情况都从原地址重新下载）;
Java服务端代码:
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protected
void
doGet(HttpServletRequest request,
HttpServletResponse response)
throws
ServletException, IOException {
// TODO Auto-generated method stub
response.setContentType(
"text/html;charset=utf-8;"
);
PrintWriter out = response.getWriter();
System.out.println(request.getParameter(
"username"
));
System.out.println(request.getParameter(
"password"
));
if
(request.getParameter(
"type"
) ==
null
) {
out.print(
"默认测试"
);
}
else
{
if
(request.getParameter(
"type"
).equals(
"async"
)) {
out.print(
"异步Get请求"
);
}
else
{
out.print(
"Get请求"
);
}
}
}
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最终效果如下:
Post请求的代码，基本跟Get类型，有注释，就不多解释了:
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//设置URL
NSURL
*url=[
NSURL
URLWithString:@
"http://localhost:8080/MyWeb/Book"
];
//创建请求
NSMutableURLRequest
*request = [[
NSMutableURLRequest
alloc]initWithURL:url cachePolicy:
NSURLRequestUseProtocolCachePolicy
timeoutInterval:10];
[request setHTTPMethod:@
"POST"
];
//设置请求方式为POST，默认为GET
NSString
*param= @
"Name=博客园&Address=http://www.cnblogs.com/xiaofeixiang&Type=post"
;//设置参数
NSData
*data = [param dataUsingEncoding:
NSUTF8StringEncoding
];
[request setHTTPBody:data];
//连接服务器
NSData
*received = [
NSURLConnection
sendSynchronousRequest:request returningResponse:
nil
error:
nil
];
NSString
*result= [[
NSString
alloc]initWithData:received encoding:
NSUTF8StringEncoding
];
NSLog
(@
"%@"
,result);
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Java服务端代码:
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protected
void
doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
request.setCharacterEncoding(
"utf-8"
);
response.setContentType(
"text/html;charset=utf-8"
);
PrintWriter out = response.getWriter();
System.out.println(
"姓名:"
+ request.getParameter(
"Name"
));
System.out.println(
"地址:"
+ request.getParameter(
"Address"
));
System.out.println(
"类型:"
+ request.getParameter(
"Type"
));
if
(request.getParameter(
"Type"
).equals(
"async"
)) {
out.print(
"异步请求"
);
}
else
{
out.print(
"Post请求"
);
}
}
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效果如下:
Get和Post异步请求
异步实现的时候需要实现协议NSURLConnectionDataDelegate，Get异步代码如下:
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//设置URL路径
NSString
*urlStr=[
NSString
stringWithFormat:@
"http://localhost:8080/MyWeb/Book?username=%@&password=%s&type=async"
,@
"FlyElephant"
,
"keso"
];
urlStr=[urlStr stringByAddingPercentEscapesUsingEncoding:
NSUTF8StringEncoding
];
NSURL
*url=[
NSURL
URLWithString:urlStr];
//创建请求
NSURLRequest
*request = [[
NSURLRequest
alloc]initWithURL:url cachePolicy:
NSURLRequestUseProtocolCachePolicy
timeoutInterval:10];
//连接服务器
NSURLConnection
*connection = [[
NSURLConnection
alloc]initWithRequest:request delegate:
self
];
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实现协议的连接过程的方法:
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-(
void
)connection:(
NSURLConnection
*)connection didReceiveResponse:(
NSURLResponse
*)response{
NSHTTPURLResponse
*res = (
NSHTTPURLResponse
*)response;
NSLog
(@
"%@"
,[res allHeaderFields]);
self
.myResult = [
NSMutableData
data];
}
////接收到服务器传输数据的时候调用，此方法根据数据大小执行若干次
-(
void
)connection:(
NSURLConnection
*)connection didReceiveData:(
NSData
*)data
{
[
self
.myResult appendData:data];
}
//数据传输完成之后执行方法
-(
void
)connectionDidFinishLoading:(
NSURLConnection
*)connection
{
NSString
*receiveStr = [[
NSString
alloc]initWithData:
self
.myResult encoding:
NSUTF8StringEncoding
];
NSLog
(@
"%@"
,receiveStr);
}
//网络请求时出现错误（断网，连接超时)执行方法
-(
void
)connection:(
NSURLConnection
*)connection didFailWithError:(
NSError
*)error
{
NSLog
(@
"%@"
,[error localizedDescription]);
}
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异步传输的过程数据需要拼接，所以这个时候需要设置一个属性接收数据:
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@property
(strong,
nonatomic
)
NSMutableData
*myResult;
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效果如下:
Post异步传递代码:
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//设置URL
NSURL
*url=[
NSURL
URLWithString:@
"http://localhost:8080/MyWeb/Book"
];
//设置请求
NSMutableURLRequest
*request = [[
NSMutableURLRequest
alloc]initWithURL:url cachePolicy:
NSURLRequestUseProtocolCachePolicy
timeoutInterval:10];
[request setHTTPMethod:@
"POST"
];
//设置请求方式为POST，默认为GET
NSString
*param= @
"Name=keso&Address=http://www.cnblogs.com/xiaofeixiang&Type=async"
;//设置参数
NSData
*data = [param dataUsingEncoding:
NSUTF8StringEncoding
];
[request setHTTPBody:data];
//连接服务器
NSURLConnection
*connection = [[
NSURLConnection
alloc]initWithRequest:request delegate:
self
];
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效果如下:
异步的请求比较简单，需要的方法都已经被封装好了，需要注意数据是动态拼接的,请求的代码都是在Java Servlet中实现的，Java项目中的目录如下:
Book.java中代码如下:
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import
java.io.IOException;
import
java.io.PrintWriter;
import
java.net.URLDecoder;
import
java.net.URLEncoder;
import
javax.servlet.ServletException;
import
javax.servlet.annotation.WebServlet;
import
javax.servlet.http.HttpServlet;
import
javax.servlet.http.HttpServletRequest;
import
javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class Book
*/
@WebServlet
(
"/Book"
)
public
class
Book
extends
HttpServlet {
private
static
final
long
serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public
Book() {
super
();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
* response)
*/
protected
void
doGet(HttpServletRequest request,
HttpServletResponse response)
throws
ServletException, IOException {
// TODO Auto-generated method stub
response.setContentType(
"text/html;charset=utf-8;"
);
PrintWriter out = response.getWriter();
System.out.println(request.getParameter(
"username"
));
System.out.println(request.getParameter(
"password"
));
if
(request.getParameter(
"type"
) ==
null
) {
out.print(
"默认测试"
);
}
else
{
if
(request.getParameter(
"type"
).equals(
"async"
)) {
out.print(
"异步Get请求"
);
}
else
{
out.print(
"Get请求"
);
}
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
* response)
*/
protected
void
doPost(HttpServletRequest request,
HttpServletResponse response)
throws
ServletException, IOException {
// TODO Auto-generated method stub
request.setCharacterEncoding(
"utf-8"
);
response.setContentType(
"text/html;charset=utf-8"
);
PrintWriter out = response.getWriter();
System.out.println(
"姓名:"
+ request.getParameter(
"Name"
));
System.out.println(
"地址:"
+ request.getParameter(
"Address"
));
System.out.println(
"类型:"
+ request.getParameter(
"Type"
));
if
(request.getParameter(
"Type"
).equals(
"async"
)) {
out.print(
"异步Post请求"
);
}
else
{
out.print(
"Post请求"
);
}
}
}
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Get和Post总结
①同步请求一旦发送，程序将停止用户交互，直至服务器返回数据完成，才可以进行下一步操作(例如登录验证)；
②异步请求不会阻塞主线程，会建立一个新的线程来操作，发出异步请求后，依然可以对UI进行操作，程序可以继续运行；
③Get请求，将参数直接写在访问路径上，容易被外界看到，安全性不高，地址最多255字节;
④Post请求，将参数放到body里面，安全性高，不易被捕获；
本文转自Fly_Elephant博客园博客，原文链接：http://www.cnblogs.com/xiaofeixiang/p/4306786.html，如需转载请自行联系原作者
