Java程序是否真的通过代理访问网络，还是准备一个代理工
作者：互联网
Java程序是否真的通过代理访问网络，还是准备一个代理工具：fiddler，很好的一个能监视http、https的debug工具，附件中有。
二. 开始
先写一段简单的网络访问程序，如下：
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URI;
import java.net.URL;
import java.net.URLConnection;
public class MyClass {
public static String ParseStream(InputStream stream) {
StringBuilder builder = new StringBuilder("");
try (BufferedReader reader = new BufferedReader(new InputStreamReader(stream))) {
String strtmp;
try {
strtmp = reader.readLine();
while (null != strtmp) {
builder.append(strtmp);
builder.append("\n");
strtmp = reader.readLine();
}
} catch (IOException e) {
e.printStackTrace();
}
} catch (Exception e) {
e.printStackTrace();
}
return builder.toString();
}
public static void main(String[] args) {
try {
URL url = new URL("http://1212.ip138.com/ic.asp");
URLConnection connection = url.openConnection();
System.out.println(ParseStream(connection.getInputStream()));
} catch (Exception e) {
e.printStackTrace();
}
}
}
同时，打开fiddler工具，运行该程序，发现fiddler中并没有任何显示，原因：jvm的网络连接会绕过fiddler的代理
所以我们要设置fiddler为本机代理服务器，IP：localhost，Port：8888
1.直接在jvm参数中设置该代理服务器
说明：http代理为 -Dhttp.proxyHost=localhost -Dhttp.proxyPort=8888，https代理为 -Dhttps.proxyHost=localhost -Dhttps.proxyPort=8888
然后再次运行上面的程序，发现fiddler中有显示，说明代理设置成功
2.代码中设置全局代理
去掉jvm参数中的代理设置，在代码中设置，如下：
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URI;
import java.net.URL;
import java.net.URLConnection;
public class MyClass {
public static String ParseStream(InputStream stream) {
StringBuilder builder = new StringBuilder("");
try (BufferedReader reader = new BufferedReader(new InputStreamReader(stream))) {
String strtmp;
try {
strtmp = reader.readLine();
while (null != strtmp) {
builder.append(strtmp);
builder.append("\n");
strtmp = reader.readLine();
}
} catch (IOException e) {
e.printStackTrace();
}
} catch (Exception e) {
e.printStackTrace();
}
return builder.toString();
}
public static void main(String[] args) {
System.setProperty("http.proxyHost", "localhost");
System.setProperty("http.proxyPort", "8888");
System.setProperty("https.proxyHost", "localhost");
System.setProperty("https.proxyPort", "8888");
try {
URL url = new URL("http://1212.ip138.com/ic.asp");
URLConnection connection = url.openConnection();
System.out.println(ParseStream(connection.getInputStream()));
} catch (Exception e) {
e.printStackTrace();
}
}
}
3.设置Proxy对象
同样是通过代码来设置，如下：
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.InetSocketAddress;
import java.net.Proxy;
import java.net.Proxy.Type;
import java.net.ProxySelector;
import java.net.SocketAddress;
import java.net.URI;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;
public class MyClass {
public static String ParseStream(InputStream stream) {
StringBuilder builder = new StringBuilder("");
try (BufferedReader reader = new BufferedReader(new InputStreamReader(stream))) {
String strtmp;
try {
strtmp = reader.readLine();
while (null != strtmp) {
builder.append(strtmp);
builder.append("\n");
strtmp = reader.readLine();
}
} catch (IOException e) {
e.printStackTrace();
}
} catch (Exception e) {
e.printStackTrace();
}
return builder.toString();
}
public static void main(String[] args) {
SocketAddress address = new InetSocketAddress("localhost", 8888);
Proxy proxy = new Proxy(Type.HTTP, address);
try {
URL url = new URL("http://1212.ip138.com/ic.asp");
URLConnection connection = url.openConnection(proxy);
System.out.println(ParseStream(connection.getInputStream()));
} catch (Exception e) {
e.printStackTrace();
}
}
}
4.基于Proxy对象的方式来设置 ProxySelector
由于单纯的设置Proxy 对象有点麻烦，每次都要设置，所以可以一次性设置所有的Proxy 对象，程序自动使用合适的Proxy 对象
通过 ProxySelector 选择器来完成，这个选择器是个抽象类，需要实现两个方法，select 方法是用于列举出你所有用到的Proxy 对象，让程序来自动选择的，这个方法
返回一个列表，意思是从列表的第一个代理开始尝试，如果第一个不行，就尝试第二个，直到最后，如果都不行就调用第二个需要实现的方法 connectFailed，即通知
程序这个链接无法通过设置的代理访问，好了，代码如下：
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.InetSocketAddress;
import java.net.Proxy;
import java.net.Proxy.Type;
import java.net.ProxySelector;
import java.net.SocketAddress;
import java.net.URI;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;
public class MyClass {
public static class MyProxy extends ProxySelector {
private List<URI> failed = new ArrayList<>();
@Override
public List<Proxy> select(URI uri) {
List<Proxy> result = new ArrayList<>();
if (failed.contains(uri) || (!"https".equalsIgnoreCase(uri.getScheme())
&& !"http".equalsIgnoreCase(uri.getScheme()))) {
result.add(Proxy.NO_PROXY);
} else {
SocketAddress address = new InetSocketAddress("localhost", 8888);
Proxy proxy = new Proxy(Type.HTTP, address);
result.add(proxy);
}
return result;
}
@Override
public void connectFailed(URI uri, SocketAddress sa, IOException ioe) {
failed.add(uri);
}
}
public static String ParseStream(InputStream stream) {
StringBuilder builder = new StringBuilder("");
try (BufferedReader reader = new BufferedReader(new InputStreamReader(stream))) {
String strtmp;
try {
strtmp = reader.readLine();
while (null != strtmp) {
builder.append(strtmp);
builder.append("\n");
strtmp = reader.readLine();
}
} catch (IOException e) {
e.printStackTrace();
}
} catch (Exception e) {
e.printStackTrace();
}
return builder.toString();
}
public static void main(String[] args) {
try {
URL url = new URL("http://1212.ip138.com/ic.asp");
URLConnection connection = url.openConnection();
System.out.println(ParseStream(connection.getInputStream()));
} catch (Exception e) {
e.printStackTrace();
}
}
}
至此
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原文链接：https://blog.csdn.net/aaa000830/article/details/78487761
标签：java,代理,new,访问,strtmp,io,import,Java,net 来源： https://www.cnblogs.com/xinxihua/p/14541250.html