Troubleshooting

If everything works fine, we don't have to worry about troubleshooting. However, most of the time this is not the case. A Maven build could fail for many reasons—some are under your control, while others are beyond your control. Knowing proper troubleshooting tips helps you pinpoint the exact problem. The following sections list out some of the commonly used troubleshooting tips. We will expand the list as we proceed in this book.

Enabling Maven debug-level logs

Once Maven debug level logging is enabled, it will print all the actions it takes during the build process. To enable debug level logging, use the following command:

$ mvn clean install –X

Building dependency tree

If you find any issues with any dependencies in your Maven project, the first step is to build a dependency tree. This shows where each dependency comes from. To build the dependency tree, run the following command against your project POM file:

$ mvn dependency:tree

The following result shows the truncated output of the previous command executed against the Apache Rampart project:

[INFO] --------------------------------------------------------------
[INFO] Building Rampart - Trust 1.6.1-wso2v12
[INFO] --------------------------------------------------------------
[INFO] 
[INFO] --- maven-dependency-plugin:2.1:tree (default-cli) @ rampart-trust ---
[INFO] org.apache.rampart:rampart-trust:jar:1.6.1-wso2v12
[INFO] +- org.apache.rampart:rampart-policy:jar:1.6.1-wso2v12:compile
[INFO] +- org.apache.axis2:axis2-kernel:jar:1.6.1-wso2v10:compile
[INFO] |  +- org.apache.ws.commons.axiom:axiom-api:jar:1.2.11-wso2v4:compile (version managed from 1.2.11)
[INFO] |  |  \- jaxen:jaxen:jar:1.1.1:compile
[INFO] |  +- org.apache.ws.commons.axiom:axiom-impl:jar:1.2.11-wso2v4:compile (version managed from 1.2.11)
[INFO] |  +- org.apache.geronimo.specs:geronimo-ws-metadata_2.0_spec:jar:1.1.2:compile
[INFO] |  +- org.apache.geronimo.specs:geronimo-jta_1.1_spec:jar:1.1:compile
[INFO] |  +- javax.servlet:servlet-api:jar:2.3:compile
[INFO] |  +- commons-httpclient:commons-httpclient:jar:3.1:compile
[INFO] |  |  \- commons-codec:commons-codec:jar:1.2:compile
[INFO] |  +- commons-fileupload:commons-fileupload:jar:1.2:compile

Viewing all environment variables and system properties

If you have multiple JDKs installed in your system, you may wonder what is being used by Maven. The following command will display all the environment variables and system properties set for a given Maven project:

$ mvn help:system

The following result is the truncated output of the previous command:

========================Platform Properties Details==================
=====================================================================
System Properties
=====================================================================

java.runtime.name=Java(TM) SE Runtime Environment
sun.boot.library.path=/System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Libraries
java.vm.version=20.65-b04-462
awt.nativeDoubleBuffering=true
gopherProxySet=false
mrj.build=11M4609
java.vm.vendor=Apple Inc.
java.vendor.url=http://www.apple.com/
guice.disable.misplaced.annotation.check=true
path.separator=:
java.vm.name=Java HotSpot(TM) 64-Bit Server VM
file.encoding.pkg=sun.io
sun.java.launcher=SUN_STANDARD
user.country=US
sun.os.patch.level=unknown

========================================================
Environment Variables
=========================================================

JAVA_HOME=/System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK/Home
HOME=/Users/prabath
TERM_SESSION_ID=9E4F0D49-180D-45F6-B6FB-DFA2DCBF4B77
M2_HOME=/usr/share/maven/maven-3.2.3/
COMMAND_MODE=unix2003
Apple_PubSub_Socket_Render=/tmp/launch-w7NZbG/Render
LOGNAME=prabath
USER=prabath

Viewing the effective POM file

Maven uses default values for the configuration parameters when those are not overridden at the project level configuration. This is exactly what we discussed under the convention over configuration section. If we take the same sample POM file we used before in this chapter, we can see how the effective POM file would look using the following command.

$ mvn help:effective-pom

This is also the best way to see what default values are being used by Maven. More details about the effective-pom command are discussed in Chapter 2, Demystifying Project Object Model.

Viewing the dependency classpath

The following command lists all the JAR files and directories in the build classpath:

$ mvn dependency:build-classpath

The following result shows the truncated output of the previous command, executed against the Apache Rampart project:

[INFO] --------------------------------------------------------------
[INFO] Building Rampart - Trust 1.6.1-wso2v12
[INFO] --------------------------------------------------------------
[INFO] 
[INFO] --- maven-dependency-plugin:2.1:build-classpath (default-cli) @ rampart-trust ---
[INFO] Dependencies classpath:
/Users/prabath/.m2/repository/bouncycastle/bcprov-jdk14/140/bcprov-jdk14-140.jar:/Users/prabath/.m2/repository/commons-cli/commons-cli/1.0/commons-cli-1.0.jar:/Users/prabath/.m2/repository/commons-codec/commons-codec/1.2/commons-codec-1.2.jar:/Users/prabath/.m2/repository/commons-collections/commons-collections/3.1/commons-collections-3.1.jar

Mastering Apache Maven 3

By : Siriwardena

Mastering Apache Maven 3

By: Siriwardena

Overview of this book

Troubleshooting

Enabling Maven debug-level logs

Building dependency tree

Viewing all environment variables and system properties

Viewing the effective POM file

Viewing the dependency classpath

Mastering Apache Maven 3

By : Siriwardena

Mastering Apache Maven 3

By: Siriwardena

Overview of this book

Troubleshooting

Enabling Maven debug-level logs

Building dependency tree

Viewing all environment variables and system properties

Viewing the effective POM file

Viewing the dependency classpath

Delete Bookmark