How do I set the proxy to be used by the JVM

Question

Many times, a Java app needs to connect to the Internet. The most common example happens when it is reading an XML file and needs to download its schema.

I am behind a proxy server. How do I set my JVM to use the proxy ?

Answer 1

From the Java documentation (not the javadoc API):

http://java.sun.com/j2se/1.5.0/docs/guide/net/properties.html

Set the JVM flags http.proxyHost and http.proxyPort when starting your JVM on the command line. This is usually done in a shell script (in Unix) or bat file (in Windows). Here's the example with the Unix shell script:

JAVA_FLAGS=-Dhttp.proxyHost=10.0.0.100 -Dhttp.proxyPort=8800
java ${JAVA_FLAGS} ...

When using containers such as JBoss or WebLogic, my solution is to edit the start-up scripts supplied by the vendor.

Many developers are familiar with the Java API (javadocs), but many times the rest of the documentation is overlooked. It contains a lot of interesting information: http://java.sun.com/j2se/1.5.0/docs/

Answer 2

You can set those flags programatically this way:

 if (needsProxy()) {
  System.getProperties().put("proxySet", "true");
  System.getProperties().put("proxyHost", getProxyHost());
  System.getProperties().put("proxyPort", getProxyPort());
 } else {
  System.getProperties().put("proxySet", "false");
  System.getProperties().put("proxyHost", "");
  System.getProperties().put("proxyPort", "");
 }

Just return the right values from the methods needsProxy(), getProxyHost() and getProxyPort() and you can call this code snippet whenever you want

Greetz, GHad

Answer 3

reading an XML file and needs to download its schema

If you are counting on retrieving schemas or DTDs over the internet, you're building a slow, chatty, fragile application. What happens when that remote server hosting the file takes planned or unplanned downtime? Your app breaks. Is that OK?

See http://xml.apache.org/commons/components/resolver/resolver-article.html#s.catalog.files

URL's for schemas and the like are best thought of as unique identifiers. Not as requests to actually access that file remotely. Do some google searching on "XML catalog". An XML catalog allows you to host such resources locally, resolving the slowness, chattiness and fragility.

It's basically a permanently cached copy of the remote content. And that's OK, since the remote content will never change. If there's ever an update, it'd be at a different URL. Making the actual retrieval of the resource over the internet especially silly.

Answer 4

Also, if you are always looking to download the same schema, then you can add the schema to your classpath (filesystem or JAR), and then use a custom EntityResolver

See here for a more complete discussion of this approach.

Edit: See @me.yahoo.com/a/0QMxE's discussion of CatalogResolver, which uses the EntityResolver approach:

CatalogResolver cr = new CatalogResolver();
...
yourParser.setEntityResolver(cr)

Answer 5

You can set some properties about the proxy server as jvm parameters

-Dhttp.proxyPort=8080, proxyHost, etc.

but if you need pass through an authenticating proxy, you need an authenticator like this example:

ProxyAuthenticator.java

import java.net.*;
import java.io.*;

public class ProxyAuthenticator extends Authenticator {

    private String userName, password;

    protected PasswordAuthentication getPasswordAuthentication() {
        return new PasswordAuthentication(userName, password.toCharArray());
    }

    public ProxyAuthenticator(String userName, String password) {
        this.userName = userName;
        this.password = password;
    }
}

Example.java

    import java.net.Authenticator;
    import ProxyAuthenticator;

public class Example {

    public static void main(String[] args) {
        String username = System.getProperty("proxy.authentication.username");
        String password = System.getProperty("proxy.authentication.password");

       if (username != null && !username.equals("")) {
            Authenticator.setDefault(new ProxyAuthenticator(username, password));
        }

       // here your JVM will be authenticated

    }
}

Based on this reply: http://mail-archives.apache.org/mod_mbox/jakarta-jmeter-user/200208.mbox/%3C494FD350388AD511A9DD00025530F33102F1DC2C@MMSX006%3E

Answer 6

To set an HTTP/HTTPS and/or SOCKS proxy programmatically:

...

public void setProxy() {
    if (isUseHTTPProxy()) {
        // HTTP/HTTPS Proxy
        System.setProperty("http.proxyHost", getHTTPHost());
        System.setProperty("http.proxyPort", getHTTPPort());
        System.setProperty("https.proxyHost", getHTTPHost());
        System.setProperty("https.proxyPort", getHTTPPort());
        if (isUseHTTPAuth()) {
            String encoded = new String(Base64.encodeBase64((getHTTPUsername() + ":" + getHTTPPassword()).getBytes()));
            con.setRequestProperty("Proxy-Authorization", "Basic " + encoded);
            Authenticator.setDefault(new ProxyAuth(getHTTPUsername(), getHTTPPassword()));
        }
    }
    if (isUseSOCKSProxy()) {
        // SOCKS Proxy
        System.setProperty("socksProxyHost", getSOCKSHost());
        System.setProperty("socksProxyPort", getSOCKSPort());
        if (isUseSOCKSAuth()) {
            System.setProperty("java.net.socks.username", getSOCKSUsername());
            System.setProperty("java.net.socks.password", getSOCKSPassword());
            Authenticator.setDefault(new ProxyAuth(getSOCKSUsername(), getSOCKSPassword()));
        }
    }
}

...

public class ProxyAuth extends Authenticator {
    private PasswordAuthentication auth;

    private ProxyAuth(String user, String password) {
        auth = new PasswordAuthentication(user, password == null ? new char[]{} : password.toCharArray());
    }

    protected PasswordAuthentication getPasswordAuthentication() {
        return auth;
    }
}

...

Remember that HTTP proxies and SOCKS proxies operate at different levels in the network stack, so you can use one or the other or both.

Answer 7

You can utilize the http.proxy* JVM variables if you're within a standalone JVM but you SHOULD NOT modify their startup scripts and/or do this within your application server (except maybe jboss or tomcat). Instead you should utilize the JAVA Proxy API (not System.setProperty) or utilize the vendor's own configuration options. Both WebSphere and WebLogic have very defined ways of setting up the proxies that are far more powerful than the J2SE one. Additionally, for WebSphere and WebLogic you will likely break your application server in little ways by overriding the startup scripts (particularly the server's interop processes as you might be telling them to use your proxy as well...).

Answer 8

Recently I've discovered the way to allow JVM to use browser proxy settings. What you need to do is to add ${java.home}/lib/deploy.jar to your project and to init the library like the following:

import com.sun.deploy.net.proxy.DeployProxySelector;
import com.sun.deploy.services.PlatformType;
import com.sun.deploy.services.ServiceManager;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

public abstract class ExtendedProxyManager {

    private static final Log logger = LogFactory.getLog(ExtendedProxyManager.class);

    /**
     * After calling this method, proxy settings can be magically retrieved from default browser settings.
     */
    public static boolean init() {
        logger.debug("Init started");

        // Initialization code was taken from com.sun.deploy.ClientContainer:
        ServiceManager
                .setService(System.getProperty("os.name").toLowerCase().indexOf("windows") != -1 ? PlatformType.STANDALONE_TIGER_WIN32
                        : PlatformType.STANDALONE_TIGER_UNIX);

        try {
            // This will call ProxySelector.setDefault():
            DeployProxySelector.reset();
        } catch (Throwable throwable) {
            logger.error("Unable to initialize extended dynamic browser proxy settings support.", throwable);

            return false;
        }

        return true;
    }
}

Afterwards the proxy settings are available to Java API via java.net.ProxySelector.

The only problem with this approach is that you need to start JVM with deploy.jar in bootclasspath e.g. java -Xbootclasspath/a:"%JAVA_HOME%\jre\lib\deploy.jar" -jar my.jar. If somebody knows how to overcome this limitation, let me know.