Spring Proxy

This small library gives you the possibility to handle proxy settings and convert these to the default java proxy system properties. This is a benefit, because a lot of libraries use the default java proxy system properties and this makes it easier to use proxies for libraries in the Spring universe. An example is the Feign Client from the Spring Cloud library that need no more settings for proxies, if this library is used.

Get Library

The library is available over the jcenter maven repository. You mast only setup the jcenter repository and use the dependency:

maven:

...
<repositories>
    <repository>
        <id>jcenter</id>
        <url>https://jcenter.bintray.com/</url>
    </repository>
</repositories>

<dependencies>
    <dependency>
        <groupId>de.baswil.spring</groupId>
        <artifactId>spring-proxy</artifactId>
        <version>1.2</version>
    </dependency>
</dependencies>
...

gradle:

...
repositories {
    jcenter()
}

dependencies {
    compile 'de.baswil.spring:spring-proxy:1.2'
}
...

Use the library

The library implements an ApplicationListener for Spring applications which handles system property, spring properties and environment variables. With Spring boot you must only change your main class from:

package de.baswil.spring.proxy.examples;

import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class ExampleProxyApplication {
  public static void main (String[] args) {
    SpringApplication.run(ExampleProxyApplication.class, args);
  }
}

to:

package de.baswil.spring.proxy.examples;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import de.baswil.spring.proxy.ProxyApplicationListener;

@SpringBootApplication
public class ExampleProxyApplication {
  public static void main (String[] args) {
    SpringApplication app = new SpringApplication(ExampleProxyApplication.class);
    app.addListeners(new ProxyApplicationListener());
    app.run(args);
  }
}

Functionality of the ProxyApplicationListener

The ProxyApplicationListener read in a first step the following environment variables:

• http_proxy
• https_proxy
• no_proxy

In the next step the listener read the following properties of the spring properties:

• http.proxyHost
• http.proxyPort
• http.proxyUser
• http.proxyPassword
• https.proxyHost
• https.proxyPort
• https.proxyUser
• https.proxyPassword
• http.nonProxyHosts

The spring application properties have a higher priority, so that these properties can override the values of the environment variables.

The Last step is to write the properties in the java system properties if they are set.

Overriding of Environment Variables

The overriding process in the ApplicationListener is designed to override only the particular set values of a proxy setting. In the following table are the environment variables and the system variables that can override this variables.

Environment Variable	System Properties
http_proxy	http.proxyHost, http.proxyPort, http.proxyUser, http.proxyPassword
https_proxy	https.proxyHost, https.proxyPort, https.proxyUser, https.proxyPassword
no_proxy	http.nonProxyHosts

If the environment variable http_proxy is set to http://username:password@localhost:8080 and in the application the property http.proxyPort is set to 9999, the resulting system properties are:

• http.proxyHost = localhost
• http.proxyPort = 9999
• http.proxyUser = username
• http.proxyPassword = password

Special behavior by no_proxy and http.nonProxyHosts

The no_proxy environment variable is a little bit tricky, because it has not the same format as the java http.nonProxyHosts system property. no_proxy has a comma (,) as delimiter that will be converted to a pipe (|) for the http.nonProxyHosts property.

Moreover there are some operation systems / tools that do not use a astrix (*) no_proxy to include all sub domains (e. g. .google.de includes all sub domains of google.de because of the leading dot). The http.nonProxyHosts property do not support this so the listener added the astrix in front of the dot.

custom format for http.nonProxyHosts application property

Sometimes the property http.nonProxyHosts contains a custom format. In such situations there are two properties for customize the parsing of the no proxy property:

• proxy-format.app-http-no-proxy.format
• proxy-format.app-http-no-proxy.formatter

proxy-format.app-http-no-proxy.format defines the format. The values OS, JAVA and OTHER are possible. The default is JAVA and do not change the value of the no proxy hosts. OS stands for the format of a normal environment variable (comma as delimiter). With OTHER you can define a custom formatter with the proxy-format.app-http-no-proxy.formatter property. This library contains some implementations:

• de.baswil.spring.proxy.noproxy.NoChangeProxyFormatter
  Same as setting proxy-format.app-http-no-proxy.format to JAVA
• de.baswil.spring.proxy.noproxy.OSNoProxyFormatter
  Same as setting proxy-format.app-http-no-proxy.format to OS
• de.baswil.spring.proxy.noproxy.OSIncludingAllSubDomainsNoProxyFormatter
  Extends the formatter de.baswil.spring.proxy.noproxy.OSNoProxyFormatter and include all sub domains of domains

All other formats are possible if you implement the de.baswil.spring.proxy.noproxy.NoProxyFormatter interface.

Unset Environment Variables

In the same way environment variables can be overridden be application properties you can unset the values. You must only set the application properties without a value (empty string).

Libraries do not use Default Java Proxy Properties

There are some libraries that do not use the default java system properties for proxy settings. In this case there two possibilities, to get the information about the set proxy settings:

Read System Properties:

System.getProperty("http.proxyHost");

Use ProxyInformation Bean:

@Configure
public class UseNoProxySettings {
  @Autowired
  private ProxyInformation proxyInformation;
}

The ProxyInformation bean has methods for all proxy settings and forwards this method call to the system properties.

Why an ApplicationListener?

An application Listener is used, because of the starting process of SpringBoot. When a SpringBoot application start, SpringBoot configure a lot of things and beans at the start or later at runtime. At this process SpringBoot do not guarantee an order of the configurations. This is the reason why an ApplicationListener is needed. The ProxyApplicationListener is run, between the ApplicationContext of the SpringBoot application was build and the application was started. So any (Auto)Configuration has the chance to get the proxy settings.