Best effort at resolving or documenting JNA dependency issues (oshi#1091)

* Document jna version override for Spring Boot

* Add JNA to dependencyManagement

Author: dbwiddis

FAQ.md

@@ -24,7 +24,7 @@ What minimum Java version is required?
 ========
 OSHI 3.x is compatible with Java 7, but will not see any added features.  
 OSHI 4.x and 5.x (planned) require minimum Java 8 compatibility, although backporting to Java 7 would not be difficult on a fork.
-OSHI 6.x's requirements have not yet been finalized but will likely require at least Java 11.  
+OSHI 6.x's requirements have not yet been finalized but will likely require at least Java 11 and leverage modules. 
 
 Which operating systems are supported?
 ========
@@ -34,6 +34,13 @@ OSHI has been implemented and tested on the following systems.  Some features ma
 * Linux (Most major distributions) Kernel 2.6 and higher
 * Unix: Solaris 11 (SunOS 5.11) / FreeBSD 10
 
+How do I resolve JNA `NoClassDefFound` errors?
+========
+OSHI uses the latest version of JNA, which may conflict with other dependencies your project (or its parent) includes. If you experience issues with `NoClassDefFound` errors for JNA artifacts, consider one or more of the following steps to resolve the conflict:
+ - Listing OSHI earlier (or first) in your dependency list 
+ - Specifying the most recent version of JNA as a dependency
+ - If you are using a parent (e.g., Spring Boot) that includes JNA as a dependency, override the `jna.version` property 
+
 What API features are not implemented on some operating systems?
 ========
 The following generally summarizes known exceptions. If you have missing data that is not on this list, please report it in an issue so we can investigate.

README.md

@@ -62,12 +62,12 @@ Downloads
 
 Usage
 -----
-We strongly recommend you use a dependency manager such as Maven or Gradle. You can [find the appropriate syntax to include OSHI here](https://search.maven.org/artifact/com.github.oshi/oshi-core/4.3.0/jar). This will add the transitive dependencies.  If you experience issues with `NoClassDefFound` errors for JNA artifacts, you might have another dependency to JNA which resolves first. Listing OSHI earlier in your dependency list will usually resolve this, or you may try manually specifying the most recent version of JNA.
+Include OSHI and its dependencies on your classpath.  We strongly recommend you add OSHI as a dependency to your project dependency manager such as Maven or Gradle. You can [find the appropriate syntax to include OSHI here](https://search.maven.org/artifact/com.github.oshi/oshi-core/4.3.0/jar). 
 
 Create a new instance of `SystemInfo` and use the getters to access additional information.
 
 You can run the [SystemInfoTest](https://github.com/oshi/oshi/blob/master/oshi-core/src/test/java/oshi/SystemInfoTest.java)
-and see the full output for your system by cloning the project and building it with [Maven](http://maven.apache.org/index.html).
+and see the full output for your system by cloning the project and building it with [Maven](http://maven.apache.org/index.html):
 
 ```
 git clone https://github.com/oshi/oshi.git && cd oshi
@@ -77,6 +77,11 @@ git clone https://github.com/oshi/oshi.git && cd oshi
   -Dexec.classpathScope="test"
 ```
 
+Note: OSHI uses the latest version of JNA, which may conflict with other dependencies your project (or its parent) includes. If you experience issues with `NoClassDefFound` errors for JNA artifacts, consider one or more of the following steps to resolve the conflict:
+ - Listing OSHI earlier (or first) in your dependency list 
+ - Specifying the most recent version of JNA as a dependency
+ - If you are using a parent (e.g., Spring Boot) that includes JNA as a dependency, override the `jna.version` property 
+
 OSHI for enterprise
 -------------------
 Available as part of the Tidelift Subscription

oshi-core/pom.xml

@@ -24,7 +24,9 @@
     SOFTWARE.
 
 -->
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 	<modelVersion>4.0.0</modelVersion>
 
 	<parent>
@@ -46,20 +48,36 @@
 	</scm>
 
 	<properties>
+		<!-- Users of the Spring Boot Starter Parent should include this property 
+			in their POM -->
 		<jna.version>5.5.0</jna.version>
 		<main.basedir>${project.parent.basedir}</main.basedir>
 	</properties>
 
+	<dependencyManagement>
+		<dependencies>
+			<!-- Due to critical nature of OSHI jna usage, set to dependency management 
+				to help influence usage -->
+			<dependency>
+				<groupId>net.java.dev.jna</groupId>
+				<artifactId>jna</artifactId>
+				<version>${jna.version}</version>
+			</dependency>
+			<dependency>
+				<groupId>net.java.dev.jna</groupId>
+				<artifactId>jna-platform</artifactId>
+				<version>${jna.version}</version>
+			</dependency>
+		</dependencies>
+	</dependencyManagement>
 	<dependencies>
 		<dependency>
 			<groupId>net.java.dev.jna</groupId>
 			<artifactId>jna</artifactId>
-			<version>${jna.version}</version>
 		</dependency>
 		<dependency>
 			<groupId>net.java.dev.jna</groupId>
 			<artifactId>jna-platform</artifactId>
-			<version>${jna.version}</version>
 		</dependency>
 	</dependencies>
 </project>