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Default Value

true

Overview of http.keepAlive

Determines if HTTP keep alive is used when a HTTP or HTTPS request is made via an api provided by the Java SDK (HttpsURLConnection or URL.openStream()).

The http.maxConnections system property determines how many connections are kept alive.

Related System Properties

Here are some other networking Java system properties:

• http.agent
• http.maxConnections
• https.protocols
• java.net.preferIPv4Stack
• java.net.preferIPv6Addresses
• java.net.useSystemProxies
• javax.net.debug
• javax.net.ssl.trustStore
• jdk.net.hosts.file
• jdk.tls.client.protocols
• jdk.tls.disabledAlgorithms
• networkaddress.cache.negative.ttl
• networkaddress.cache.ttl
• sun.net.client.defaultConnectTimeout
• sun.net.client.defaultReadTimeout
• sun.net.inetaddr.ttl

Supported Since

Java has supported the http.keepAlive system property since at least version 1.6, support may go back to even older versions of java.

Setting http.keepAlive on Startup

You can set the http.keepAlive java system property during startup of the java runtime using the -D command line argument:

java -Dhttp.keepAlive=true MyAppMain

You may also be able to specify http.keepAlive via the JAVA_TOOL_OPTIONS environment variable:

JAVA_TOOL_OPTIONS=-Dhttp.keepAlive=true

Setting / Reading http.keepAlive at Runtime

You can set http.keepAlive at runtime with the following Java code:

System.setProperty("http.keepAlive", "true");

WARNING: Depending on the property and JVM version using setProperty may or may not work if the JDK Java class that uses this variable has already been loaded. The value of the http.keepAlive system property may be cached within an internal private static variable of the implementing class.

To read the value of http.keepAlive at runtime, you can use this Java code:

String propertyValue = System.getProperty("http.keepAlive");
if (propertyValue != null) {
    System.out.println("http.keepAlive = " + propertyValue);
} else {
    System.out.println("http.keepAlive was null");
}

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