Java 缓存机制实现：高效处理网络请求
package Intent;
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.Socket;
import java.util.ArrayList;
import java.util.Objects;
import ui.MainFrame;
public class Cache {
private Socket socket;
private MainFrame mainFrame;
private String CacheDir = null;
final static String CRLF = "\r\n";
private String thefilename;
public Cache(Socket socket, MainFrame mainFrame, String CacheDir) {
this.socket = socket;
this.mainFrame = mainFrame;
this.CacheDir = CacheDir + "\";
init();
}
void init() {
try {
InputStream is = socket.getInputStream();
DataOutputStream os = new DataOutputStream(socket.getOutputStream());
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String requestLine = br.readLine();
if(null==requestLine) {
return;
}
// Display the request line.
mainFrame.Messageappend(" ");
mainFrame.Messageappend(requestLine);
String type = requestLine.split(" ")[0];
String url = requestLine.split(" ")[1];
System.out.println(type);
System.out.println(url);
switch (type) {
case "GET": {
System.out.println("GET");
if (!url.startsWith("http"))
url = "http://" + url;
if (fileIsNeedUpdate(url)) {//判断更新文件 条件get
byte[] filecon = WritetoFile(url);
WriteToClient(is, os, filecon);
} else {
String web[] = getfilenameAndDirName(url);
String webDirname = web[0];
String webfilename = web[1];
thefilename = webfilename;
String filePath = CacheDir + webDirname + transferWebfilename(webfilename);
System.out.println(filePath);
WriteToClient(is, os, ReadFile(filePath));
}
break;
}
default:
break;
}
os.close();
br.close();
socket.close();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
private String contentType(String fileName) {
String defaultContentType = "text/html";
if(Objects.isNull(fileName)) {
return defaultContentType;
}
if (fileName.endsWith(".htm") || fileName.endsWith(".jsp") || fileName.endsWith(".php")
|| fileName.endsWith(".aspx") || fileName.endsWith(".html")) {
return "text/html";
}
if (fileName.endsWith(".css")) {
return "text/css";
}
if (fileName.endsWith(".js")) {
return "application/x-javascript";
}
if (fileName.endsWith(".jpg") || fileName.endsWith(".jpeg")) {
return "image/jpeg";
}
if (fileName.endsWith(".png")) {
return "image/png";
}
if (fileName.endsWith(".ico")) {
return "image/x-icon";
}
if (fileName.indexOf(".") == -1) {
return "text/html";
}
return defaultContentType;
}
private boolean fileIsNeedUpdate(String url) {//更新文件
String[] web = getfilenameAndDirName(url);
String webfilename = CacheDir + web[0] + web[1];
webfilename = transferWebfilename(webfilename);
System.out.println(webfilename + "_____________________________");
if (!(new File(webfilename).exists())) {
System.out.println("本记录从缓存读取");
return true;
} else
return false;
}
private String[] getfilenameAndDirName(String url) {
/**
* 根据url返回要创建的文件名和目录名
*/
String webName = url.split(":")[1];
String dirlist[] = webName.split("//");
String dd[] = dirlist[dirlist.length - 1].split("/");
String webfilename = dd[dd.length - 1];
if (webfilename.endsWith("/"))
webfilename = webfilename.substring(0, webfilename.length() - 1);
String webDirname = dirlist[1];
System.out.println(webDirname + "_______" + webfilename);
if (webDirname.startsWith(webfilename) || !webfilename.contains("."))
webfilename = "index.html";
else {
webDirname = webDirname.substring(0, webDirname.length() - webfilename.length());
}
System.out.println(webDirname + "_______" + webfilename);
return new String[] { webDirname, webfilename };
}
private byte[] ReadFile(String filepath) {
ArrayList<Byte> list = new ArrayList<Byte>();
File file = new File(filepath);
DataInputStream datainput = null;
try {
datainput = new DataInputStream(new FileInputStream(file));
} catch (FileNotFoundException e) {
e.printStackTrace();
}
ByteArrayOutputStream outStream = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = -1;
try {
while ((len = datainput.read(buffer)) != -1) {
outStream.write(buffer, 0, len);
for (int i = 0; i < len; i++)
list.add(new Byte(buffer[i]));
}
} catch (IOException e) {
e.printStackTrace();
}
Byte[] str = (Byte[]) list.toArray(new Byte[list.size()]);
byte[] thefilebyte = new byte[str.length];
for (int i = 0; i < str.length; i++)
thefilebyte[i] = str[i].byteValue();
return thefilebyte;
}
private byte[] WritetoFile(String url) {
Byte[] str = null;
String web[] = getfilenameAndDirName(url);
String webDirname = web[0];
String webfilename = web[1];
boolean if404;
try {
ArrayList<Byte> list = GetContentUrl.getUrlContent(url);//运用动态数组储存
str = (Byte[]) list.toArray(new Byte[list.size()]);
if(null == str) {
return null;
}
} catch (IOException e1) {
e1.printStackTrace();
}
byte[] thefilebyte = new byte[str.length];
try {
if404 = false;
webfilename = transferWebfilename(webfilename);
File webDir = new File(CacheDir + webDirname);
if (!webDir.exists() && !webDir.isDirectory()) {//不存在就创建
boolean success = webDir.mkdirs();
System.out.println("已创建" + webDirname + "\" + webfilename + "目录" + webDir.getPath());//cache存储的路径
}
System.out.println("地址" + webDir.getPath());
File fileWritter = new File(webDir.getPath() + "/" + webfilename);//cache存储路径的地址和文件名
DataOutputStream bufferWritter = new DataOutputStream(new FileOutputStream(fileWritter));
for (int i = 0; i < str.length; i++)
thefilebyte[i] = str[i].byteValue();
bufferWritter.write(thefilebyte);
bufferWritter.close();
thefilename = webfilename;
System.out.println("缓存成功");
} catch (IOException e) {
System.out.println(e.getMessage());
if404 = true;
}
System.out.println();
return thefilebyte;
}
private void WriteToClient(InputStream is, DataOutputStream os, byte[] request) {
String statusLine = null;
String contentTypeLine = null;
String entityBody = null;
String requestLine = null;
if (request != null) {
statusLine = "HTTP/1.1 200 OK" + CRLF;
contentTypeLine = "Content-type: " + contentType(thefilename) + CRLF;
} else {
statusLine = "HTTP/1.1 404 Not Found" + CRLF;
contentTypeLine = "Content-type: " + contentType(thefilename) + CRLF;
entityBody = "<!DOCTYPE html><html><head><title>404 Not Found</title></head><body><h1 >404 Not Found</h1><hr/>"
+ "<p style=\"font-size:30px;\">Sorry!<Br/>该请求没有找到页面, Please Check Your URL Input!</p>"
+ "</body></html>";
mainFrame.Messageappend(contentTypeLine);
}
try {
os.writeBytes(statusLine);
os.writeBytes(contentTypeLine);
os.writeBytes(CRLF);
if (request != null) {
os.write(request);
} else {
os.writeBytes(entityBody);
}
} catch (IOException e) {
e.printStackTrace();
}
}
private String transferWebfilename(String webfilename) {
return webfilename.replace("?", "");
}
}
解释代码
内容：这段代码是一个用于实现缓存功能的类。它接受一个Socket对象、一个MainFrame对象和一个缓存目录路径作为参数，用于处理从客户端发送过来的请求，并将响应结果返回给客户端。
在init()方法中，首先读取客户端发送的请求行，根据请求类型进行相应的处理。当前只处理GET请求，其他请求类型可以在switch语句中进行扩展。
在fileIsNeedUpdate()方法中，根据URL判断文件是否需要更新。如果文件不存在，则需要更新。如果文件存在，则不需要更新。
在getfilenameAndDirName()方法中，根据URL获取要创建的文件名和目录名。如果URL以http开头，则从URL中提取出目录名和文件名；否则，将URL作为文件名，并将目录名置为空字符串。
在ReadFile()方法中，从指定文件路径读取文件，并将文件内容以字节数组的形式返回。
在WritetoFile()方法中，通过GetContentUrl类获取URL对应的文件内容，并将文件内容写入缓存目录中。如果文件不存在，则创建目录并写入文件；如果文件已存在，则直接返回。
在WriteToClient()方法中，根据请求结果，构造响应的状态行、内容类型行和实体体，并将响应结果写入到客户端。
最后，在init()方法中关闭输入流、输出流和Socket连接。
这段代码实现了基本的缓存功能，通过判断文件是否需要更新，减少了对网络资源的请求，提高了响应速度。同时，通过将文件内容写入本地缓存，可以减少对网络资源的依赖，提高了程序的稳定性。
原文地址: https://www.cveoy.top/t/topic/pTyx 著作权归作者所有。请勿转载和采集!