如何解决浏览器为什么不请求数据?java的ServerSocket和套接字
最近,我想验证计算机网络问题。因此,我编写了一个程序,起初它起作用了。但有时,它会产生错误-内存不足错误。经过测试,我发现我的代码是错误的。我直接读取一个字节,然后将其转换为字符。我不知道为什么有时连接中没有数据。该程序只读取-1,然后将-1转换为字符,但是整个程序无法停止。所以,我想知道,此错误的原因是什么?我不知道是浏览器还是程序。希望您能帮助我解决这个问题。
这是我的代码:
def main():
for file_json in os.listdir(path_to_json):
if not file_json.endswith('.json'): continue
print("""""######starting######""")
print(file_json)
try:
with open("{}/{}".format(path_to_json,file_json),'r') as json_file:
json_data = json.load(json_file)
print("JSON File is Valid")
flowVersions = json_data['flow']['flowVersions']
get_status(flowVersions)
source(flowVersions)
operators(flowVersions)
target(flowVersions)
except Exception as e :
print (e)
print("JSON File is Invalid")
def get_status(flowVersions):
for flow in flowVersions:
print("status is : ",flow["status"])
def source(flowVersions):
for flow in flowVersions:
for topic in flow['topics']:
name = topic['name']
print('sourceName is : ',name)
sourceName_check = name.startswith('ES_')
if sourceName_check:
print("sourceName is vaild and starts with ES_:")
else:
print("sourceName is not starting with ES_:")
当我使用浏览器访问http:// localhost:8080时,如果您多次访问 或过一会儿,会出现错误。而且,这是错误信息:
package org.dragon;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.charset.StandardCharsets;
public class CheckServer {
public static final String CRLF = "\r\n";
public static final String BLANK = " ";
public static void main(String[] args) {
try (ServerSocket server = new ServerSocket(8080)) {
while (true) {
Socket client = server.accept();
new Thread(()-> {
StringBuilder sb = new StringBuilder();
try {
InputStream in = new BufferedInputStream(client.getInputStream());
OutputStream out = new BufferedOutputStream(client.getOutputStream());
char ch;
while ((ch = (char) in.read()) != '\n') {
sb.append(ch);
}
System.out.println(sb);
byte[] body = "I love you yesterday and today!".getBytes();
// create response header
StringBuilder headerBuilder = new StringBuilder();
headerBuilder.append("HTTP/1.1 200 OK").append(CRLF)
.append("Host:").append(BLANK).append(client.getInetAddress().getHostName()).append(CRLF)
.append("Content-Type:").append(BLANK).append("application/json").append(CRLF)
.append("Access-Control-Allow-Origin:").append(BLANK).append("*").append(CRLF)
.append("Content-Length:").append(BLANK).append(body.length).append(CRLF)
.append(CRLF);
System.out.println(headerBuilder);
// response header
byte[] header = headerBuilder.toString().getBytes(StandardCharsets.UTF_8);
// return response message
out.write(header);
out.write(body);
// flush the stream
out.flush();
} catch (Throwable e) {
e.printStackTrace();
System.out.println("StringBuilder object's length: " + sb.length());
System.out.println("StringBuilder object's content: ");
System.out.println(sb);
System.out.println("========================");
} finally {
if (client != null) {
try {
client.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}).start();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
当我尝试打印sb时,会发生异常,但是我认为这不是问题。 我真的想知道为什么代码不读取数据?
GET / HTTP/1.1
HTTP/1.1 200 OK
Host: 0:0:0:0:0:0:0:1
Content-Type: application/json
Access-Control-Allow-Origin: *
Content-Length: 31
java.lang.OutOfMemoryError: Java heap space
StringBuilder object's length: 1207959550
StringBuilder object's content:
at java.util.Arrays.copyOf(Arrays.java:3332)
at java.lang.AbstractStringBuilder.ensureCapacityInternal(AbstractStringBuilder.java:124)
at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:649)
at java.lang.StringBuilder.append(StringBuilder.java:202)
at org.dragon.CheckServer.lambda$0(CheckServer.java:28)
at org.dragon.CheckServer$$Lambda$1/135721597.run(Unknown Source)
at java.lang.Thread.run(Thread.java:748)
Exception in thread "Thread-1" java.lang.OutOfMemoryError: Java heap space
at java.util.Arrays.copyOfRange(Arrays.java:3664)
at java.lang.String.<init>(String.java:207)
at java.lang.StringBuilder.toString(StringBuilder.java:407)
at java.lang.String.valueOf(String.java:2994)
at java.io.PrintStream.println(PrintStream.java:821)
at org.dragon.CheckServer.lambda$0(CheckServer.java:56)
at org.dragon.CheckServer$$Lambda$1/135721597.run(Unknown Source)
at java.lang.Thread.run(Thread.java:748)
浏览器发送的请求是否为空?
注意::我知道我无法直接将读取的字节转换为字符。我必须判断它是否为-1。如果为-1,则可以忽略它。但是我不明白为什么会有这样的要求?
解决方法
无限的stringbuilder
按照编写的方式,您的代码从线上读取数据并将其添加到stringbuilder中,这是内存中的东西。
您的代码将继续执行此操作,直到遇到字符\n
。请注意,read()
方法将返回-1,并且如果流已结束,它将永远永远这样做。这意味着您将永远向字符串生成器添加-1
个字符的无穷序列。当然,“永远”并不是永远不变:一旦用尽内存来存储-1的无限序列,就会得到这个。
解决方案很简单:当.read()调用返回-1或\ n时,停止循环。将结果保存在局部变量中,然后可以简单地进行检查。像这样:
while (true) {
int ch = in.read(); // do NOT cast to char,you can't detect -1 that way
if (ch == -1 || ch == '\n') break;
sb.append((char) ch); // cast here.
}
不要忽略-1-在-1处结束循环。没有更多数据了。 曾经。如果您正在等待换行符,它将永远不会发生。
好的,为什么会这样?
嘿,这是网络。您没有任何保证。
版权声明:本文内容由互联网用户自发贡献,该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 dio@foxmail.com 举报,一经查实,本站将立刻删除。