CS/BS模式

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#服务器 #clientserver #数据库

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本文介绍了计算机从集中式到分布式计算模式的转变，重点关注C/S和B/S架构。C/S模式在早期广泛使用，随着Web技术的发展，B/S模式成为主流。文中讲解了B/S模式中客户端的角色，以及GET和POST两种HTTP方法在客户端与服务器交互中的应用，并提供了相关代码示例。

这里写图片描述

介绍

随着PC机的诞生与应用，计算模式从集中式（数据和应用程序在一台主机上）转向了分布式（数据和应用程序跨越多个节点机），尤为典型的是C/S结构（Client/Server的简称，客户机/服务器模式)。两层结构C/S模式，在上个世纪八十年代及九十年代初得到了大量应用,最直接的原因是可视化开发工具的推广。之后，它开始向三层结构发展。近来，随着网络技术不断发展，尤其是基于Web的信息发布和检索技术、Java计算技术以及网络分布式对象技术的飞速发展，导致了很多应用系统的体系结构从C/S结构向更加灵活的多级分布结构演变，使得软件系统的网络体系结构跨入一个新阶段，即B/S体系结构（Browser/Server的简称，浏览器/服务器模式）。基于Web的B/S方式其实也是一种客户机/服务器方式，只不过它的客户端是浏览器。为了区别于传统的C/S模式，才特意将其称为B/S（浏览器/服务器）模式。

结合今天知识点

Client

以下几个方法，相当于客户端，在做界面时用到了类 JFrame了解请点击！
界面的文本输入，按钮等都可以在这里面实现。
1、doGet
直接连接在url后面是显示的
GET 调用用于获取服务器信息，并将其做为响应返回给客户端。当经由Web浏览器或通过HTML、JSP直接访问Servlet的URL时，一般用GET调用。 GET调用在URL里显示正传送给SERVLET的数据，这在系统的安全方面可能带来一些问题，比如用户登录，表单里的用户名和密码需要发送到服务器端，若使用Get调用，就会在浏览器的URL中显示用户名和密码。

测试方法代码：

public class DoGet extends JFrame {

    private JPanel contentPane;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    DoGet frame = new DoGet();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public DoGet() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 350, 320);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);
        contentPane.setLayout(null);

        JButton btnDoget = new JButton("doGet方法测试");
        btnDoget.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                String urlString = "http://localhost:8080/MyServiceTest/MyTest?username=李三&password=11114";
            //直接跟在url后是doGet方法
                try {
                    URL url = new URL(urlString);//生成URL
                    URLConnection connect = url.openConnection();//打开url连接
                    HttpURLConnection httpConnection = (HttpURLConnection) connect;//HttpUrlConnection 是sun封装成的网络连接
                    httpConnection.setRequestMethod("GET");//设置请求方法
                    httpConnection.setConnectTimeout(3000);//设置连接超时的时间
                    httpConnection.setReadTimeout(3000);//读取时间超时
                    // 设置编码方式，接受的数据类型
                    httpConnection.setRequestProperty("Accept-Charset", "utf-8");//使用utf-8编码格式将字节数组转化成字符串
                    // 设置可以接受序列化的java对象
                    httpConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
                    int code = httpConnection.getResponseCode();//得到状态码
                    System.out.println(code);
                    if(code==HttpURLConnection.HTTP_OK){//网络连接状态成功，那么下面读数据
                        InputStream is = httpConnection.getInputStream();
                        BufferedReader br = new BufferedReader(new InputStreamReader(is));
                        String line = br.readLine();
                        while(line!=null){
                            System.out.println(line);
                            line = br.readLine();
                        }
                    }
                } catch (MalformedURLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                catch (SocketTimeoutException e) {
                    System.out.println("连接超时");
                    // TODO: handle exception
                } 
                catch (ConnectException e) {
                    System.out.println("连接失败");
                    // TODO: handle exception
                }
                catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        });
        btnDoget.setBounds(101, 86, 135, 98);
        contentPane.add(btnDoget);
    }
}

2.HttpClientDoGet
HttpClient 是apache使用httpUrlConnection封装的类
方法的测试
代码如下：

public class HttpClinetdoGet extends JFrame {

    private JPanel contentPane;
    private JTextField textFieldUsername;
    private JTextField textFieldPassword;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    HttpClinetdoGet frame = new HttpClinetdoGet();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public HttpClinetdoGet() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 310, 301);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);

        JButton btnNewButton = new JButton("New button");//按钮
        btnNewButton.setBounds(95, 150, 93, 76);
        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                String username = textFieldUsername.getText();//输入界面输入用户名和密码
                String password = textFieldPassword.getText();
                String urlString = "http://localhost:8080/MyServiceTest/MyTest?username="+username+"&password="+password+"";

                HttpClientBuilder builder = HttpClientBuilder.create(); // 生成client的builder
                builder.setConnectionTimeToLive(3000, TimeUnit.MILLISECONDS);
                HttpClient client = builder.build();//生成client
                HttpGet get = new HttpGet(urlString);//设置为get方法
                //设置服务器接收后数据的读取方式为utf-8
                get.setHeader("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8");

                try {
                    HttpResponse response = client.execute(get);//执行get方法得到服务器的返回的所有数据都在response中
                    StatusLine statusLine = response.getStatusLine();//httpClient访问服务器返回的表头，包含http状态码
                    int code = statusLine.getStatusCode();//得到状态码
                    if (code == HttpURLConnection.HTTP_OK) {
                        HttpEntity entity = response.getEntity();//得到数据的实体
                        InputStream is = entity.getContent();//得到输入流
                        BufferedReader br = new BufferedReader(new InputStreamReader(is));
                        String line = br.readLine();
                        while (line != null) {
                            System.out.println(line);
                            line = br.readLine();
                        }
                    }
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

            }
        });
        contentPane.setLayout(null);
        contentPane.add(btnNewButton);

        textFieldUsername = new JTextField();
        textFieldUsername.setBounds(107, 40, 66, 21);
        contentPane.add(textFieldUsername);
        textFieldUsername.setColumns(10);

        textFieldPassword = new JTextField();
        textFieldPassword.setBounds(107, 104, 66, 21);
        contentPane.add(textFieldPassword);
        textFieldPassword.setColumns(10);
    }
}

这里写图片描述
3、DoPost
它用于客户端把数据传送到服务器端，也会有副作用。但好处是可以隐藏传送给服务器的任何数据。Post适合发送大量的数据。
主要Java代码如下：

JButton btnPost = new JButton("Post方法测试");
        btnPost.setBounds(84, 140, 152, 90);
        btnPost.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                String urlString = "http://localhost:8080/MyServiceTest/MyTest";
                //直接跟在url后是doGet方法
                    try {
                        URL url = new URL(urlString);//生成URL
                        URLConnection connect = url.openConnection();//打开url连接
                        HttpURLConnection httpConnection = (HttpURLConnection) connect;
                        httpConnection.setRequestMethod("POST");//设置请求方法
                        httpConnection.setConnectTimeout(30000);//设置连接超时的时间
                        httpConnection.setReadTimeout(30000);//读取时间超时
                        // 设置编码方式，接受的数据类型
                        httpConnection.setRequestProperty("Accept-Charset", "UTF-8");
                        // 设置可以接受序列化的java对象
                        httpConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
                        httpConnection.setDoInput(true);//设置可以读取服务器返回的内容，默认是true
                        httpConnection.setDoOutput(true);//设置客户端可以给服务器提交数据，默认是false。post方法必须设置为true
                        httpConnection.setUseCaches(false);//post方法不允许使用缓存
                        String username = textFieldUsername.getText();
                        String password = textFieldPassowrd.getText();
                        String params = "username="+username+"&password="+password;
                        //String params = "username=lisi&password=1234";
                        httpConnection.getOutputStream().write(params.getBytes());
                        int code = httpConnection.getResponseCode();
                        System.out.println(code);
                        if(code==HttpURLConnection.HTTP_OK){
                            InputStream is = httpConnection.getInputStream();
                            BufferedReader br = new BufferedReader(new InputStreamReader(is));
                            String line = br.readLine();
                            while(line!=null){
                                System.out.println(line);
                                line = br.readLine();
                            }
                        }
                    } catch (MalformedURLException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    catch (SocketTimeoutException e) {
                        System.out.println("连接超时");
                        // TODO: handle exception
                    } 
                    catch (ConnectException e) {
                        System.out.println("连接失败");
                        // TODO: handle exception
                    }
                    catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }

            }
        });
        contentPane.setLayout(null);
        contentPane.add(btnPost);

这里写图片描述
4、HttpClientDoPost
主要Java代码如下

JButton btnNewButton = new JButton("New button");
        btnNewButton.addActionListener(new ActionListener() {
            /* (non-Javadoc)
             * @see java.awt.event.ActionListener#actionPerformed(java.awt.event.ActionEvent)
             */
            public void actionPerformed(ActionEvent e) {
                String url = "http://localhost:8080/MyServiceTest/MyTest";
                HttpClientBuilder builder = HttpClientBuilder.create(); // 生成client的builder
                builder.setConnectionTimeToLive(3000, TimeUnit.MILLISECONDS);
                HttpClient client = builder.build();//生成client
                HttpPost post = new HttpPost(url);
                NameValuePair pair1 = new BasicNameValuePair("username", "小孩");
                NameValuePair pair2 = new BasicNameValuePair("password", "123456");
                ArrayList<NameValuePair> params = new ArrayList<>();
                params.add(pair1);
                params.add(pair2);
                try {
                    post.setEntity(new UrlEncodedFormEntity(params,"UTF-8"));
                    post.setHeader("Content", "application/x-www-form-urlencoded;charser=UTF-8");
                    HttpResponse response = client.execute(post);
                    int code = response.getStatusLine().getStatusCode();
                    if(code==200){
                        HttpEntity entity = response.getEntity();
                        InputStream is = entity.getContent();
                        BufferedReader br = new BufferedReader(new InputStreamReader(is));
                        String line = br.readLine();
                        if(line!=null){
                            System.out.println(line);
                            line = br.readLine();
                        }
                    }

                } catch (UnsupportedEncodingException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                } catch (ClientProtocolException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                } catch (IOException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
            }
        });
        btnNewButton.setBounds(114, 145, 93, 55);
        contentPane.add(btnNewButton);

Servlet

1、首先要有SQLManager类，与数据库建立连接

public class SQLManager {
    private Statement statement;
    private Connection con;

    public Connection getCon() {
        return con;
    }

    public void setCon(Connection con) {
        this.con = con;
    }

    public Statement getStatement() {
        return statement;
    }

    public void setStatement(Statement statement) {
        this.statement = statement;
    }

    private static SQLManager manager;

    public static synchronized SQLManager newInstance() {
        if (manager == null) {
            manager = new SQLManager();
        }
        return manager;
    }

    private SQLManager() {
        // 导入数据库jar的驱动
        String driver = "com.mysql.jdbc.Driver";
        // URL指向要访问的数据库名
        String url = "jdbc:mysql://localhost:3306/clazz";
        // mysql配置时的用户名
        String user = "root";
        // Java连接mysql配置时的密码
        String password = "123456";

        try {
            Class.forName(driver);// 加载驱动
            con = DriverManager.getConnection(url, user, password);// 与数据库建立连接
            // 数据库操作类
            statement = con.createStatement();
            System.out.println("执行完成");
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

2、为了防止出现乱码，建立一个转码类

public class Encoding {//这个类是用来转码，就不会出现乱码了
     public static String doEncoding(String string){
         try {
            byte[] array = string.getBytes("ISO-8859-1");//接口
            string = new String(array,"UTF-8");
        } catch (UnsupportedEncodingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
         return string;

     }
}

3、Servlet类


/**
 * Servlet implementation class MyTest
 */
@WebServlet("/MyTest")
public class MyTest extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public MyTest() {
        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
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        username = Encoding.doEncoding(username);//转码
        String s = "用户名：" + username + " 密码：" + password;
        System.out.println(s);
        Connection con = SQLManager.newInstance().getCon();

        try {
            if (!con.isClosed()) {
                PreparedStatement state = con.prepareStatement("select * from user where user_name=? and password=?");
                state.setString(1, username);
                state.setString(2, password);
                ResultSet set = state.executeQuery();
                set.last();
                int num = set.getRow();
                System.out.println("查询结果：" + num);
                if(num==1){
                    System.out.println("登陆成功");
                }else{
                    System.out.println("用户名或密码错误");
                }
            }

        } catch (SQLException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
//      try {
//          Thread.sleep(10000);
//      } catch (InterruptedException e) {
//          // TODO Auto-generated catch block
//          e.printStackTrace();
//      }
        response.setHeader("Content-type", "text/html;charset=UTF-8");
        response.getWriter().append(s);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}