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Packaging jar file with source code using Maven so breakpoints can be used in Eclipse

Requirements
I am refactoring a Java application and am trying to move code out of a war file and into a jar file so it can be used across many different web applications. However, one of the requirements is that the developers still need to use breakpoints within the library. To do so I believe I need to package the source with the compiled code. Below is the build lifecycle
Build Lifecycle
<build>
<pluginManagement><!-- lock down plugins versions to avoid using Maven
defaults (may be moved to parent pom) -->
<plugins>
<!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
<plugin>
<artifactId>maven-clean-plugin</artifactId>
<version>3.1.0</version>
</plugin>
<!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
<plugin>
<artifactId>maven-resources-plugin</artifactId>
<version>3.0.2</version>
</plugin>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
</plugin>
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.22.1</version>
</plugin>
<plugin>
<artifactId>maven-jar-plugin</artifactId>
<version>3.0.2</version>
</plugin>
<plugin>
<artifactId>maven-install-plugin</artifactId>
<version>2.5.2</version>
</plugin>
<plugin>
<artifactId>maven-deploy-plugin</artifactId>
<version>2.8.2</version>
</plugin>
<!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
<plugin>
<artifactId>maven-site-plugin</artifactId>
<version>3.7.1</version>
</plugin>
<plugin>
<artifactId>maven-project-info-reports-plugin</artifactId>
<version>3.0.0</version>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-source-plugin</artifactId>
<executions>
<execution>
<id>attach-sources</id>
<goals>
<goal>jar</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</pluginManagement>
</build>
Question
When I run mvn package and mvn source:jar package it creates two jar files, respectively
db-0.0.1-SNAPSHOT.jar
db-0.0.1-SNAPSHOT-sources.jar
Then I can attach the source to the dependency.
My question is two-fold
Is there anyway to package the source code into the same jar file as the compiled classes, and
Would this auto-attach the source code to the dependency in Eclipse, so that the developers don't need to do it automatically?

Putting the source code into the JAR is the wrong approach.
You create two JARs (as shown in your question). These JARs go to the repository. Then everyone who uses the JARS will automatically get the -sources as well. In the usual IDEs, like Eclipse and IntelliJ the -sources JAR is automatically used for debugging.
Instead of two Maven runs, you should add the source plugin to your POM. Then the -sources JAR is created during the normal build.

JavaDoc can't add custom stylesheet from src/main/resources

While executing mvn javadoc:javadoc i get this error:
An error has occurred in JavaDocs report generation: Option <stylesheet/> supports only "maven" or "java" value. -> [Help 1]"
But i read here http://maven.apache.org/plugins/maven-javadoc-plugin/examples/stylesheet-configuration.html that <stylesheetfile/> could be a resource in your project directory, i.e. src/main/java, src/main/resources or src/main/javadoc
so why i can not have in my pom:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin</artifactId>
<version>2.10.4</version>
<configuration>
<stylesheet>src/main/resources/example.css</stylesheet>
</configuration>
</plugin>
?

If you like to configure a file which should be used you have to use the following configuration:
<project>
...
<reporting> (or <build>)
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin</artifactId>
<version>2.10.4</version>
<configuration>
<stylesheetfile>${basedir}/path/to/your/stylesheetfile.css</stylesheetfile>
...
</configuration>
</plugin>
</plugins>
...
</reporting> (or </build>)
...
</project>

I had a typo not <stylesheet> but <stylesheetfile> should be used.

maven exclude tests with surefire excludeTests option

I have a large project with sub-projects and want to use excludesFile to exclude test failures, and ignore them until the tests are fixed.
I believe there might be a way of achieving this with surefire plugin excludesFile option here.
I am very new to maven and would like get some examples or pointers on how this can be achieved.

To use excludesFile option,
Create a file containing file name patterns of your test files that you want to exclude.Example:Create a file at src/main/resources/exclude.txt with below 2 lines.
**/*1.java
**/*2.java
Add following in your maven-surefile-plugin configuration.
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.20</version>
<configuration>
<excludesFile>src/test/resources/exclude.txt</excludesFile>
</configuration>
</plugin>
</plugins>
You are done. All test files ending with 1.java and 2.java will be excluded.
There is other way also to exclude any tests from execution by using configuration in maven-surefire-plugin.
Example:
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.20</version>
<configuration>
<excludes>
<exclude>**/TestCircle.java</exclude>
<exclude>**/TestSquare.java</exclude>
</excludes>
</configuration>
</plugin>
</plugins>
More information can be found here.

FindBugs: How can I run it in Java 5 mode?

When I run FindBugs on my project via Maven, I get lots of these:
Can't use annotations when running in JDK 1.4 mode!
How do I fix that? Couldn't find anything in the manual.

I believe you are missing the targetJdk element in the plugin configuration, like in below snippet.
<reporting>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>findbugs-maven-plugin</artifactId>
<version>2.0.1</version>
<configuration>
<targetJdk>1.5</targetJdk>
</configuration>
</plugin>
</plugins>
</reporting>

Make sure your Maven build plugin is compiling to 1.5, and not 1.4.
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.5</source>
<target>1.5</target>
</configuration>
</plugin>

Maven project dependency against JDK version

I have projects that need to be build with a specific version of the JDK.
The problem isn't in the source and target parameters but in the jars of the runtime used during compilation.
In some cases I get a compilation error if I try to compile with the wrong JDK, but sometimes the build is successful and I get runtime errors when using the jars.
For example in eclipse I have the ability to establish the execution enviroment for the project in the .classpath file.
Is there a way to handle such situation in maven?
What I would like to have is the ability to handle JRE dependency like other dependencies of the project in the POM file.
UPDATE:
The accepted solution was the best one when I asked this question, so I won't change it. Meanwhile a new solution to this kind of problems has been introduced: Maven Toolchain. Follow the link for further details.

I've found this article:
http://maven.apache.org/plugins/maven-compiler-plugin/examples/compile-using-different-jdk.html
<project>
[...]
<build>
[...]
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.1</version>
<configuration>
<verbose>true</verbose>
<fork>true</fork>
<executable>${JAVA_1_4_HOME}/bin/javac</executable>
<compilerVersion>1.3</compilerVersion>
</configuration>
</plugin>
</plugins>
[...]
</build>
[...]
</project>

I have projects that need to be build with a specific version of the JDK.
You can use the Maven Enforcer plugin to enforce the use of a particular version of the JDK:
<project>
[...]
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-enforcer-plugin</artifactId>
<executions>
<execution>
<id>enforce-versions</id>
<goals>
<goal>enforce</goal>
</goals>
<configuration>
<rules>
<requireJavaVersion>
<version>1.5</version>
</requireJavaVersion>
</rules>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
[...]
</project>
But I'm not sure I really understood the question. If this is not what you want, maybe you could declare your JDK specific dependencies in profiles and use an activation trigger based on the JDK version. For example:
<profiles>
<profile>
<activation>
<jdk>1.5</jdk>
</activation>
...
</profile>
</profiles>
This configuration will trigger the profile when the JDK's version starts with "1.5".

I believe that this can be solved with following plugin in your pom:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.1</version>
<configuration>
<source>1.6</source>
<target>1.6</target>
</configuration>
</plugin>
Here you target version 1.6 , or write your own version