xcode get link json format from server api

Question

I try to Separate data to：

NSLog(@"shelf_id=%@", shelf_id);
NSLog(@"http_url=%@", http_url);
NSLog(@"shelf_date=%@", shelf_date);

I get start _date and end_date for server ,then server give me json format

This is my code:

+ (NSString* ) loadCoverPage {
    NSString *urlStr = [NSString stringWithFormat:@"http://apps.play.com/iphone/porfile/get_pic_list.jsp?start_date=%@& end_date=%@", [CalTools getValueforKey:@"SelectYMD" DefValue:@""], [CalTools getValueforKey:@"SelectYMD" DefValue:@""]];

    NSLog(@"loadpicbg url=%@", urlStr);
    HttpTools *httpTools = [[HttpTools alloc] init];
    NSString *returnstr = [httpTools simpleGet:urlStr];
    NSLog(@"returnstr = %@", returnstr);        
}

This is my link json format from server api:

[{"size":1},{"shelf_id":"1","http_url":"http://down.play.com/shelf/pic/jpg/640x960/64.jpg","shelf_date":"20120601"}];