（五）——Response

package my.tomcat2;

import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.util.Date;

/**
 * 用来反馈客户端，也就是想在客户端上显示什么信息
 */
public class Response {
    //构建 响应头信息需要的一些小零件，这里可以在网上查看下 HTTP 协议
    private static final String CRLF = "\r\n";
    private static final String BLANK = " ";
    //这里是正文，也就是显示在页面上的信息
    private StringBuilder context;
    //这里是构建 响应头信息
    private StringBuilder headInfo;
    //因为头信息最后会需要 正文的 字节长度，是字节长度，不是字符长度
    private int len;
    //用来反馈到客户端上的 输出流
    private BufferedWriter bw;
    private String msg;
    //状态码，这里如上查询 HTTP 协议
    private int code;

    //初始化 字段
    public Response(Socket client) {
        context = new StringBuilder();
        headInfo = new StringBuilder();
        try {
            bw = new BufferedWriter(new OutputStreamWriter(client.getOutputStream()));
        } catch (IOException e) {
            code = 500;
            return ;
        }
    }


    //构建 响应头部信息
    public void setHead(int code){
        headInfo.append("HTTP/1.1").append(BLANK).append(code).append(BLANK);
        switch (code) {
            case 200 : headInfo.append("OK").append(CRLF);
                break;

            case 404 : headInfo.append("NOT FOUND").append(CRLF);
                break;

            case 500 : headInfo.append("SERVER ERROR").append(CRLF);
                break;
        }
        headInfo.append("Server:Feng server/0.01").append(CRLF);
        headInfo.append("Date:").append(new Date()).append(CRLF);
        headInfo.append("Content-type:text/html;charset=utf-8").append(CRLF);
        headInfo.append("Content-Length:" + len).append(CRLF);
        headInfo.append(CRLF);
    }

    //反馈给 客户端 的信息
    public void print(String msg){
        context.append(msg);
        len += msg.getBytes().length;
    }

    public void println(String msg){
        context.append(msg).append(CRLF);
        len += (msg+CRLF).getBytes().length;
    }
    
    //将 响应头信息+正文 通过流传给 客户端
    public void pushToClient(int code){
        if(context == null){
            code = 500;
        }
        this.setHead(code);
        String responseInfo = headInfo.append(context).toString();
        try {
            bw.write(responseInfo);
            bw.flush();
        } catch (IOException e) {
            return ;
        } finally {
            CloseUtil.close(bw);
        }
    }
}