1.GET请求解释及语法格式:
网络请求默认是get
网络请求有很多种：GET查 POST改 PUT增 DELETE删 HEAD
在平时开发中主要用的 是 get 和 post.
get 获得数据 （获取用户信息）
get 请求是没有长度限制的，真正的长度限制是浏览器做的，限制长度一般2k
get 请求是有缓存的,get 有幂等的算法
请求参数暴露在url里
get请求参数格式：
？后是请求参数
参数名 = 参数值
& 连接两个参数的
POST请求解释及语法格式:
get请求参数格式：
？后是请求参数
参数名 = 参数值
& 连接两个参数的
post 添加，修改数据 （上传或修改用户信息）
post 请求是没有缓存的
post 也没有长度限制，一般控制2M以内
post 请求参数不会暴漏在外面 ，不会暴漏敏感信息
请求是有：请求头header，请求体boby（post参数是放在请求体里的）
GET请求代码
NSString *userName = @"haha"; NSString *password = @"123"; NSString *urlString = @"http://192.168.1.68/login.php"; //防止请求体中含有中文 urlString = [urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]; //?号是请求参数 注意username和password一定要和你的php页面的登录id相同 NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"%@?username=%@&password=%@",urlString,userName,password]]; //cachePolicy 缓存策略 0表示自动缓存 timeoutInterval: 默认请求时间60s，通常设置为10-30秒之间 NSURLRequest *requst = [NSURLRequest requestWithURL:url cachePolicy:0 timeoutInterval:0]; // response是服务器返回信息: 里面有所用时间，服务器的型号等..... [NSURLConnection sendAsynchronousRequest:requst queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) { NSString *string = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding]; NSLog(@"%@",string); }]; POST请求代码 NSString *userName = @"haha"; NSString *password = @"123"; NSString *urlString = @"http://192.168.1.68/login.php"; urlString = [urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]; NSURL *url = [NSURL URLWithString:urlString]; //可变请求，因为是post请求所以要用NSMutableURLRequest NSMutableURLRequest *requst = [NSMutableURLRequest requestWithURL:url cachePolicy:0 timeoutInterval:10]; requst.HTTPMethod = @"POST"; NSString *bodyString = [NSString stringWithFormat:@"username=%@&password=%@",userName,password]; //POST请求不写这个会访问失败-直接显示非法请求 requst.HTTPBody = [bodyString dataUsingEncoding:NSUTF8StringEncoding]; [NSURLConnection sendAsynchronousRequest:requst queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) { NSString *string = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding]; NSLog(@"%@",string); }];
2.通过设置响应头来实现下载功能
<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>Insert title here</title> </head> <body> <a href="download?filename=1366768.jpg">下载图片</a> <a href="download?filename=1366.jpg">下载图片</a> <a href="download?filename=你好.txt">下载中文名称文档</a> </body> </html>
public class DownLoadServlet extends HttpServlet {
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String filename = request.getParameter("filename");
File f = new File(this.getServletContext().getRealPath("download/"+filename));//获取服务器资源
if(f.exists()) {//解决文件名中文问题
String agent = request.getHeader("user-agent");
if (agent.contains("MSIE")) {
// IE浏览器
filename = URLEncoder.encode(filename, "utf-8");
filename = filename.replace("+", " ");
} else if (agent.contains("Firefox")) {
// 火狐浏览器
BASE64Encoder base64Encoder = new BASE64Encoder();
filename = "=?utf-8?B?"
+ base64Encoder.encode(filename.getBytes("utf-8")) + "?=";
} else {
// 其它浏览器
filename = URLEncoder.encode(filename, "utf-8");
}
response.setContentType(this.getServletContext().getMimeType(f.getPath()));//设置页面文件类型
response.setHeader("Content-Disposition", "attachment;filename="+filename);//以附件方式打开文件
ServletOutputStream sos = response.getOutputStream();
FileInputStream fis = new FileInputStream(f);
int len = 0;
byte[] b = new byte[1024];
while((len=fis.read(b))!=-1) {
sos.write(b,0,len);
}
fis.close();
}else {
response.setContentType("text/html;charset=utf-8");//解决响应中文问题
response.getWriter().println("<h2 style='color:red;'>文件不存在！</h2>");
}
}
@Override
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
3.验证码生成
public class CheckImgServlet extends HttpServlet {
// 集合中保存所有成语
private List<String> words = new ArrayList<String>();
@Override
public void init() throws ServletException {
// 初始化阶段，读取new_words.txt
// web工程中读取 文件，必须使用绝对磁盘路径
String path = getServletContext().getRealPath("/WEB-INF/new_words.txt");
try {
BufferedReader reader = new BufferedReader(new FileReader(path));
String line;
while ((line = reader.readLine()) != null) {
words.add(line);
}
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 禁止缓存
// response.setHeader("Cache-Control", "no-cache");
// response.setHeader("Pragma", "no-cache");
// response.setDateHeader("Expires", -1);
int width = 120;
int height = 30;
// 步骤一 绘制一张内存中图片
BufferedImage bufferedImage = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);
// 步骤二 图片绘制背景颜色 ---通过绘图对象
Graphics graphics = bufferedImage.getGraphics();// 得到画图对象 --- 画笔
// 绘制任何图形之前 都必须指定一个颜色
graphics.setColor(getRandColor(200, 250));
graphics.fillRect(0, 0, width, height);
// 步骤三 绘制边框
graphics.setColor(Color.WHITE);
graphics.drawRect(0, 0, width - 1, height - 1);
// 步骤四 四个随机数字
Graphics2D graphics2d = (Graphics2D) graphics;
// 设置输出字体
graphics2d.setFont(new Font("宋体", Font.BOLD, 18));
Random random = new Random();// 生成随机数
int index = random.nextInt(words.size());
String word = words.get(index);// 获得成语
// 定义x坐标
int x = 10;
for (int i = 0; i < word.length(); i++) {
// 随机颜色
graphics2d.setColor(new Color(20 + random.nextInt(110), 20 + random
.nextInt(110), 20 + random.nextInt(110)));
// 旋转 -30 --- 30度
int jiaodu = random.nextInt(60) - 30;
// 换算弧度
double theta = jiaodu * Math.PI / 180;
// 获得字母数字
char c = word.charAt(i);
// 将c 输出到图片
graphics2d.rotate(theta, x, 20);
graphics2d.drawString(String.valueOf(c), x, 20);
graphics2d.rotate(-theta, x, 20);
x += 30;
}
// 将验证码内容保存session
request.getSession().setAttribute("checkcode_session", word);
// 步骤五 绘制干扰线
graphics.setColor(getRandColor(160, 200));
int x1;
int x2;
int y1;
int y2;
for (int i = 0; i < 30; i++) {
x1 = random.nextInt(width);
x2 = random.nextInt(12);
y1 = random.nextInt(height);
y2 = random.nextInt(12);
graphics.drawLine(x1, y1, x1 + x2, x2 + y2);
}
// 将上面图片输出到浏览器 ImageIO
graphics.dispose();// 释放资源
//将图片写到response.getOutputStream()中
ImageIO.write(bufferedImage, "jpg", response.getOutputStream());
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
/**
* 取其某一范围的color
*
* @param fc
* int 范围参数1
* @param bc
* int 范围参数2
* @return Color
*/
private Color getRandColor(int fc, int bc) {
// 取其随机颜色
Random random = new Random();
if (fc > 255) {
fc = 255;
}
if (bc > 255) {
bc = 255;
}
int r = fc + random.nextInt(bc - fc);
int g = fc + random.nextInt(bc - fc);
int b = fc + random.nextInt(bc - fc);
return new Color(r, g, b);
}
}