HttpClient NoClassDefFoundError

Question

I am trying to run a sample application from HttpClient 4.0.1. It is the file ClientMultiThreadedExecution.java from the examples section. I put in these files in the classpath: apache-mime4j-0.6.jar;commons-codec-1.3.jar;commons-logging-1.1.1.jar;httpclient-4.0.1.jar;httpcore-4.0.1.jar;httpmime-4.0.1.jar and the file compiles correctly. At runtime I get the following error:

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/http/client/methods/HttpUriRequest
Caused by: java.lang.ClassNotFoundException: org.apache.http.client.methods.HttpUriRequest
    at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
    at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)

Am I missing a reference? It seems like a classpath error but I can't figure out which jar file to include? Thank you in advance for your help.

Answer 1

This exception tells that the mentioned class is missing in the runtime classpath.

There are several ways to specify the runtime classpath, depending on how you're executing the program. Since a decent IDE takes this all transparently from your hands, I bet that you're running it in a command prompt.

If you're running it as a JAR file by java.exe -jar or doubleclicking the file, then you need to specify the classpath in the Class-Path entry of the JAR's MANIFEST.MF file. Note that the %CLASSPATH% environment variable and -cp and -classpath arguments are ignored whenever you execute a JAR.

If you're running it as a "plain vanilla" Java application by java.exe, then you need to specify it in the -cp or -classpath argument. Note that whenever you use this argument, the %CLASSPATH% environment variable is ignored.

Either way, the classpath should exist of a (semi)colonseparated string of paths to JAR files (either absolute paths or relative to current working directory). E.g.

java -cp .;/path/to/file1.jar;/path/to/file2.jar com.example.MyClass

(if you're on Unix/Linux, use colon instead of semicolon as path separator)