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Default Value

Empty - By default debug logging is not enabled

Overview of javax.net.debug

The javax.net.debug system property enables debug logging for Java Secure Socket Extension or JSSE connections make by java applications using the SunJSSE provider. This includes connections made using the SSL or TLS protocols such as HTTPS connections.

The debugging output produced by the javax.net.debug property is not logged to a file. Instead the output is printed to System.out.

Usage Examples

You can combine multiple values in a comma separated list or colon separated list.

-Djavax.net.debug=ssl,handshake,data,keymanager

The above will output (to System.out) SSL/TLS handshake hex dumps, and keymanager tracing information.

Possible javax.net.debug Values

• all - prints all JSSE debugging info
• ssl - prints all debugging info related to SSL (or TLS). The following sub options exist within ssl:
  • record - enable per-record tracing
    • plaintext - output hex dumps of record plaintext
    • packet - output raw SSL/TLS packets
  • handshake - output each SSL/TLS handshake message
    • data - Hex dump of each handshake message
    • verbose - verbose handshake message printing
  • keygen - output key generation info
  • session - output session info
  • defaultctx - output default SSL initialization
  • sslctx - enable SSLContext tracing
  • sessioncache - enable session cache tracing
  • keymanager - enable key manager tracing
  • trustmanager - enable trust manager tracing

References

• JSSE Reference Guide

Related System Properties

Here are some other networking Java system properties:

• http.agent
• http.keepAlive
• http.maxConnections
• https.protocols
• java.net.preferIPv4Stack
• java.net.preferIPv6Addresses
• java.net.useSystemProxies
• 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 javax.net.debug system property since at least version 1.8, support may go back to even older versions of java.

Setting javax.net.debug on Startup

You can set the javax.net.debug java system property during startup of the java runtime using the -D command line argument:

java -Djavax.net.debug=all MyAppMain

You may also be able to specify javax.net.debug via the JAVA_TOOL_OPTIONS environment variable:

JAVA_TOOL_OPTIONS=-Djavax.net.debug=all

Setting / Reading javax.net.debug at Runtime

You can set javax.net.debug at runtime with the following Java code:

System.setProperty("javax.net.debug", "all");

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 javax.net.debug system property may be cached within an internal private static variable of the implementing class.

To read the value of javax.net.debug at runtime, you can use this Java code:

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

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