Response類

??? ex01.pyrmont.Response類代表一個HTTP響應，在Listing 1.6里邊給出。
???????? Listing 1.6: Response類

package ex01.pyrmont;
import java.io.OutputStream;
import java.io.IOException;
import java.io.FileInputStream;
import java.io.File;
/*
HTTP Response = Status-Line
*(( general-header | response-header | entity-header ) CRLF)
CRLF
[ message-body ]
Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF
*/
public class Response {
???? private static final int BUFFER_SIZE = 1024;
???? Request request;
???? OutputStream output;
???? public Response(OutputStream output) {
???????? this.output = output;
???? }
???? public void setRequest(Request request) {
???????? this.request = request;
???? }
???? public void sendStaticResource() throws IOException {
???????? byte[] bytes = new byte[BUFFER_SIZE];
???????? FileInputStream fis = null;
???????? try {
???????????? File file = new File(HttpServer.WEB_ROOT, request.getUri());
???????????? if (file.exists()) {
???????????????? fis = new FileInputStream(file);
???????????????? int ch = fis.read(bytes, 0, BUFFER_SIZE);
???????????????? while (ch!=-1) {
???????????????????? output.write(bytes, 0, ch);
???????????????????? ch = fis.read(bytes, 0, BUFFER_SIZE);
???????????????? }
???????????? }
???????????? else {
???????????? // file not found
???????????? String errorMessage = "HTTP/1.1 404 File Not Found\r\n" +
???????????????? "Content-Type: text/html\r\n" +
???????????????? "Content-Length: 23\r\n" +
???????????????? "\r\n" +
???????????????? "<h1>File Not Found</h1>";
???????????? output.write(errorMessage.getBytes());
???????????? }
???????? }
???????? catch (Exception e) {
???????????? // thrown if cannot instantiate a File object
???????????? System.out.println(e.toString() );
???????? }
???????? finally {
???????????? if (fis!=null)
???????????? fis.close();
???????? }
???? }
}

??? 首先注意到它的構造方法接收一個java.io.OutputStream對象，就像如下所示。

public Response(OutputStream output) {
???? this.output = output;
}

??? 響應對象是通過傳遞由套接字獲得的OutputStream對象給HttpServer類的await方法來構造的。Response類有兩個公共方法：setRequest和sendStaticResource。setRequest方法用來傳遞一個Request對象給Response對象。
??? sendStaticResource方法是用來發送一個靜態資源，例如一個HTML文件。它首先通過傳遞上一級目錄的路徑和子路徑給File累的構造方法來實例化java.io.File類。

File file = new File(HttpServer.WEB_ROOT, request.getUri());

??? 然后它檢查該文件是否存在。假如存在的話，通過傳遞File對象讓sendStaticResource構造一個java.io.FileInputStream對象。然后，它調用FileInputStream的read方法并把字節數組寫入OutputStream對象。請注意，這種情況下，靜態資源是作為原始數據發送給瀏覽器的。

if (file.exists()) {
???? fis = new FileInputstream(file);
???? int ch = fis.read(bytes, 0, BUFFER_SIZE);
???? while (ch!=-1) {
???????? output.write(bytes, 0, ch);
???????? ch = fis.read(bytes, 0, BUFFER_SIZE);
???? }
}

??? 假如文件并不存在，sendStaticResource方法發送一個錯誤信息到瀏覽器。

String errorMessage =
???? "Content-Type: text/html\r\n" +
???? "Content-Length: 23\r\n" +
???? "\r\n" +
???? "<h1>File Not Found</h1>";
output.write(errorMessage.getBytes());

轉載于:https://www.cnblogs.com/macula7/archive/2009/08/16/1960791.html

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