背景
有時候我們會有些特別的想法：
- 查看或動態(tài)修改網(wǎng)絡的請求與返回的參數(shù)
- 實現(xiàn)自己的緩存規(guī)則
原理
NSURLProtocol可以用于數(shù)據(jù)請求和數(shù)據(jù)返回的攔截與修改。具體工作流程，如下。
具體工作流程
需要了解一下URL Loading System（ULS）工作原理。每當我們發(fā)出一個請求的時候，ULS會詢問NSURLProtocol注冊的子類是否需要攔截，需要攔截的話，處理完，再扔回ULS詢問。為了避免這個問題，每次攔截完之后，需要標記一下已攔截過，下次再詢問就不要再攔截了。
注意事項
- NSURLSession需要注意：對于基于NSURLSession的網(wǎng)絡請求，需要通過配置NSURLSessionConfiguration對象的protocolClasses屬性。
NSURLSessionConfiguration *sessionConfiguration = [NSURLSessionConfiguration defaultSessionConfiguration];
sessionConfiguration.protocolClasses = @[[NSClassFromString(@"CustomURLProtocol") class]];
- NSURLConnection：直接registerClass就可以用
擴展
iOS - 讓WKWebView 支持 NSURLProtocol
最后附上您可能用得著的代碼
攔截修改請求的一個類
//RSURLProtocol.h
#import <Foundation/Foundation.h>
NS_ASSUME_NONNULL_BEGIN
@interface RSURLProtocol : NSURLProtocol
+ (void)requestConfig;
@end
NS_ASSUME_NONNULL_END
//RSURLProtocol.m
#import "RSURLProtocol.h"
#import "RSDataHandle.h"
#import <objc/runtime.h>
#import <UIKit/UIKit.h>
#import "ConsoleHelper.h"
#import "RSInfo.h"
static NSString * const RSURLConfig = @"http://xxx.com/config";
static NSString * const RSURLProtocolHandledKey = @"RSURLProtocolHandledKey";
@interface RSURLProtocol()<NSURLSessionDelegate>
@property (nonatomic,strong) NSURLSession *session;
@end
@implementation RSURLProtocol
+(void)load{
[RSURLProtocol registerProtocol];
[self injectNSURLSessionConfiguration];
[self requestConfig];
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
[[ConsoleHelper sharedInstance] show];
});
}
+ (NSString *)finalConfigString{
if ([RSInfo.sharedInstance.networkAppID length]>0) {
return [NSString stringWithFormat:@"%@?appID=%@",RSURLConfig,RSInfo.sharedInstance.networkAppID];
}
return RSURLConfig;
}
+ (void)requestConfig{
RSInfo.sharedInstance.configInit = false;
NSURLSession *session = [NSURLSession sharedSession];
NSURL *url = [NSURL URLWithString:[self finalConfigString]];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
[[session dataTaskWithRequest:request completionHandler:^(NSData*_Nullable data, NSURLResponse*_Nullable response, NSError*_Nullable error) {
if(!error) {
// 數(shù)據(jù)請求成功
NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:nil];
if (dic && [dic[@"code"] intValue]==0) {
[RSInfo sharedInstance].configs = dic[@"data"];
RSInfo.sharedInstance.configInit = true;
}
} else {
// 數(shù)據(jù)請求失敗
}
}] resume];
}
+ (void)injectNSURLSessionConfiguration{
Class cls = NSClassFromString(@"__NSCFURLSessionConfiguration") ?: NSClassFromString(@"NSURLSessionConfiguration");
Method originalMethod = class_getInstanceMethod(cls, @selector(protocolClasses));
Method stubMethod = class_getInstanceMethod([self class], @selector(rs_protocolClasses));
if (!originalMethod || !stubMethod) {
[NSException raise:NSInternalInconsistencyException format:@"Couldn't load NEURLSessionConfiguration."];
}
method_exchangeImplementations(originalMethod, stubMethod);
}
- (NSArray *)rs_protocolClasses {
return @[[RSURLProtocol class]];
}
+ (void)registerProtocol
{
[NSURLProtocol registerClass:[self class]];
}
+ (void)unregisterProtocol
{
[NSURLProtocol unregisterClass:[self class]];
}
#pragma mark - 攔截處理
+ (BOOL)canInitWithRequest:(NSURLRequest *)request
{
if ([NSURLProtocol propertyForKey:RSURLProtocolHandledKey inRequest:request]) {
return NO;
}
// 攔截http、https
NSString * scheme = [[request.URL scheme] lowercaseString];
if ([scheme isEqual:@"http"]||[scheme isEqual:@"https"]) {
return YES;
}
return NO;
}
//?這個方法用來統(tǒng)一處理請求request 對象的，可以修改頭信息，或者重定向。沒有特殊需要，則直接return request。
//??如果要在這里做重定向以及頭信息的時候注意檢查是否已經(jīng)添加，因為這個方法可能被調(diào)用多次，也可以在后面的方法中做。
+ (NSURLRequest *)canonicalRequestForRequest:(NSURLRequest *)request {
return request;
}
//主要判斷兩個request是否相同，如果相同的話可以使用緩存數(shù)據(jù)，通常只需要調(diào)用父類的實現(xiàn)。
+ (BOOL)requestIsCacheEquivalent:(NSURLRequest *)a toRequest:(NSURLRequest *)b {
return [super requestIsCacheEquivalent:a toRequest:b];
}
//在攔截到網(wǎng)絡請求，并且對網(wǎng)絡請求進行定制處理以后。我們需要將網(wǎng)絡請求重新發(fā)送出去，就可以初始化一個NSURLProtocol對象了：
- (id)initWithRequest:(NSURLRequest *)request cachedResponse:(NSCachedURLResponse *)cachedResponse client:(id <NSURLProtocolClient>)client {
return [super initWithRequest:request cachedResponse:cachedResponse client:client];
}
- (void)reStartRequest {
[RSDataHandle handleRequest:[self request]];
NSMutableURLRequest *mutableReqeust = [[self request] mutableCopy];
//標示該request已經(jīng)處理過了，防止無限循環(huán)
[NSURLProtocol setProperty:@(YES) forKey:RSURLProtocolHandledKey inRequest:mutableReqeust];
//使用NSURLSession繼續(xù)把request發(fā)送出去
NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
NSOperationQueue *mainQueue = [NSOperationQueue mainQueue];
self.session = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:mainQueue];
NSURLSessionDataTask *task = [self.session dataTaskWithRequest:mutableReqeust];
[task resume];
}
//實際請求
- (void)startLoading
{
if (RSInfo.sharedInstance.configInit || [[RSURLProtocol finalConfigString] isEqualToString:[self request].URL.absoluteString]) {
[self reStartRequest];
}else{
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
[self startLoading];
});
}
}
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler
{
[self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
completionHandler(NSURLSessionResponseAllow);
}
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data
{
// 打印返回數(shù)據(jù)
NSString *dataStr = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
if (dataStr) {
NSLog(@"***截取URL***: %@", dataTask.currentRequest.URL.absoluteString);
NSLog(@"***截取數(shù)據(jù)***: %@", dataStr);
dataStr = [RSDataHandle handleResponse:dataStr url:dataTask.currentRequest.URL];
if (dataStr) {
[self.client URLProtocol:self didLoadData:[dataStr dataUsingEncoding:NSUTF8StringEncoding]];
return ;
}
}
[self.client URLProtocol:self didLoadData:data];
}
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
{
if (error) {
[self.client URLProtocol:self didFailWithError:error];
} else {
[self.client URLProtocolDidFinishLoading:self];
}
}
- (void)stopLoading {
[self.session invalidateAndCancel];
self.session = nil;
}
@end
