I'm trying to use the Base 64 functions present in the Apache Commons Codec package. I'm using Leiningen, and have this in my project.clj:
:dependencies [[org.clojure/clojure "1.2.0"]
[commons-codec/commons-codec "1.4"]]
Leiningen successfully finds the appropriate .jar. I can't for the life of me figure out which class I actually need to import, though. I have tried all variations of
(ns my-project.core
(:import (org.apache.commons.codec.binary Base64)))
but nothing seems to work. What class name should I be using for this?
I would recommend cutting to the chase and checking where the rubber hits the road. Make sure Leiningen did in fact place the correct jar in the lib directory of your project. Open the jar and look inside and see of the class you are looking for is there. If the path to that class in the jar should match the path of your import statement.
Whoops. It looks like I was just calling the class itself incorrectly. The following worked fine after the :import line above: (.decode (Base64.) s). Thanks for the responses, everyone.
Related
I am following this tutorial: https://practicalli.github.io/blog/posts/web-scraping-with-clojure-hacking-hacker-news/ and I have had a hard time dealing with the :require part of the ns macro. This tutorial shows how to parse HTML and pull out information from it with a library called enlive, and to use it, I first had to put
...
:dependencies [[org.clojure/clojure "1.10.1"]
[enlive "1.1.6"]]
...
in my project.clj, and require the library in core.clj as the following:
(ns myproject.core
(:require [net.cgrand.enlive-html :as html])
(:gen-class))
I spent so much time finding out the name net.cgrand.enlive-html, since it was different from the package's name itself (which is just enlive), and I couldn't find it through any of the lein commands (I eventually found it out by googling).
How can I easily find out what name to require?
Practical approach
If your editor/IDE helps with auto-completion and
docs, that might be a first route.
Other than that, libraries usually have some read-me online, where they show off
what they do (what to require, how to use that).
Strict approach
If you really have nothing about a library, you will find the downloaded
library in you ~/.m2/repository directory. Note that deps without the naming
convention of "group/artifact" will just double on the artifact name, Next is
the version. So you can find your libraries JAR file here:
.m2/repository/enlive/enlive/1.1.6/enlive-1.1.6.jar.
JAR files are just ZIP-Files. Inside the JAR file you will usually find the
source files of the library. The directory structure reflects the package
structure. E.g. one file there is net/cgrand/enlive_html.clj (note the use
of the _ instead of -, this is due to name munging for the JVM). You then
can require the file in your REPL and explore with doc or dir etc. Or you
open this file, to see the docs and source code in one chunk.
Usually I get this from the documentation / tutorial for the library.
https://github.com/cgrand/enlive Check out the Quick Tutorial, which starts with the needed require.
I am using lein repl without a project so there is no project.clj.
I am running Leiningen 2.8.1 on Java 1.8.0_191 OpenJDK 64-Bit Server VM.
When I require a Clojure dependency that I assume should just work - like clojure.data.json - I notice that it is not in my .m2 directory. Is that why I am getting a FileNotFoundException Could not locate clojure/data/json__init.class or clojure/data/js
on.clj on classpath? I can't find my other Clojure dependencies there either so I don't know where they reside and if this dependancy should be in .m2 or not.
I understand the error message but without knowing its location or even knowing how to properly add it to the CLASSPATH for the REPL to see it, I remain stuck.
Is this a dependency that I still need to install? If so, how do I install it without going through a project?
I don't understand the JVM as I am new to it, so add a little extra information in your answer.
I have looked at this, this, this, this and this. I don't know if I am overlooking anything so your help will really be appreciated.
I am using lein run without a project so there is no project.clj.
If you're using Leiningen, this'll be much easier if you create a project.clj file that declares your dependencies. Leiningen will read project.clj and handle fetching any missing dependencies to your local Maven repository, and add them to your classpath when you start your REPL/application. (lein run doesn't work for me in a directory without a project.clj; I get an error: No :main namespace specified in project.clj.. Did you mean lein repl?)
When I require a Clojure dependency that I assume should just work - like clojure.data.json - I notice that it is not in my .m2 directory.
clojure.data.json doesn't ship with Clojure — it's a separate dependency that must be fetched and added to your classpath in order to use it. The classpath tells the JVM where to look when it loads class files. Leiningen will do both of these things for you if you declare the dependency in project.clj:
:dependencies [[org.clojure/clojure "1.10.0"]
[org.clojure/data.json "0.2.6"]]
You can also use the lein deps command if you only want to fetch dependencies.
You can create a new/blank Leiningen project with lein new project_name_goes_here. It will have a project.clj with a few boilerplate entries and a :dependencies key where you can declare dependencies.
I understand the error message but without knowing its location or even knowing how to properly add it to the CLASSPATH for the REPL to see it, I remain stuck. Is this a dependency that I still need to install? If so, how do I install it without going through a project?
You could manually download it from the internet, then manually add its path to your classpath, but if you're already using Leiningen it's much easier to add a line to a project.clj file and have Leiningen handle this for you.
If using a project.clj file w/Leiningen isn't an option, there are other ways to use Clojure and resolve dependencies/build a classpath at runtime. Boot accommodates this workflow, you can use Leiningen like this with a little added effort, as well as the newer tools.deps tooling. There are examples of each in this ClojureVerse thread, but note that some of these approaches are doing essentially the same thing as declaring the dependency in a file — instead declaring them as CLI arguments.
For example, using Clojure CLI tooling:
$ clj -Sdeps "{:deps {org.clojure/data.json {:mvn/version \"0.2.6\"}}}"
Clojure 1.9.0
user=> (require '[clojure.data.json :as json])
nil
user=> (json/write-str {:foo "bar"})
"{\"foo\":\"bar\"}"
user=> (System/getProperty "java.class.path")
"src:
/Users/me/.m2/repository/org/clojure/clojure/1.9.0/clojure-1.9.0.jar:
/Users/me/.m2/repository/org/clojure/data.json/0.2.6/data.json-0.2.6.jar:
/Users/me/.m2/repository/org/clojure/spec.alpha/0.1.143/spec.alpha-0.1.143.jar:
/Users/me/.m2/repository/org/clojure/core.specs.alpha/0.1.24/core.specs.alpha-0.1.24.jar"
You could create a deps.edn file containing {:deps {org.clojure/data.json {:mvn/version \"0.2.6\"}}} in the same directory, and clj would read that, resolve the dependencies if necessary, and build the classpath accordingly.
This is a great opportunity to use lein try. Once you add it to your ~/.lein/profiles.clj, you'd simply run: lein try org.clojure/data.json and you'll be greeted with a running REPL with that dependency just a require away.
I want to check if Windows ENV variable http_proxy is picked properly by Leiningen. I've found a function get-proxy-settings but can't understand how to call it properly. Seems I have to use namespace leiningen.core.classpath somehow for this?
This is my second day to learn Clojure and I am not familiar with namespaces yet.
Just try your proxy settings in your environment and see if it works. It should work automatically.
But if you must, you can call leiningen.core.classpath/get-proxy-settings from your project definition by using unquote. Minimal example:
(defproject proxy-settings "0.1-SNAPSHOT"
:dependencies [[org.clojure/clojure "1.8.0"]]
:plugins [[lein-pprint "1.1.2"]]
:debug/proxy ~(leiningen.core.classpath/get-proxy-settings))
Note the lein-pprint plugin there.
Use lein pprint to see the value of :debug/proxy.
Solution
(1) (println (. System getProperty "java.library.path"))
This gives me a list of places java looks for native extensions.
Then, I took the lwjgl native extensions, and put them there.
Things that didn't work for me (probably because I used them incorrectly)
(*) setting :native-path
(*) setting :native-dependencies
Problem
My setup:
(lein deps; echo "====="; cat project.clj; echo "====="; cat src/main.clj; echo "====="; lein repl) &> log
contents of "log"
Copying 10 files to /Volumes/ramdisk/fail/lib
=====
(defproject
mincase "0.0.1"
:dependencies [[org.clojure/clojure "1.4.0"]
[org.lwjgl.lwjgl/lwjgl "2.8.2"] ]
:repositories {"local" "/Users/x/z/maven_repo"}
:jvm-opts ["-Xms4g" "-Xmx4g"]
:repl-init main
)
=====
(ns main
(:import org.lwjgl.opengl.Display))
=====
REPL started; server listening on localhost port 31235
UnsatisfiedLinkError no lwjgl in java.library.path java.lang.ClassLoader.loadLibrary (ClassLoader.java:1860)
clojure.core=>
Note -- I had already done a "lein deps", so the lwjgl library has been pulled into maven. What I don't understand are:
(*) how do I get access to lwjgl from Clojure?
(*) more importantly, how do I debug which step this whole thing has gone wrong at?
$ find lib
lib
lib/clojure-1.4.0.jar
lib/jinput-2.0.5.jar
lib/jinput-platform-2.0.5-natives-linux.jar
lib/jinput-platform-2.0.5-natives-osx.jar
lib/jinput-platform-2.0.5-natives-windows.jar
lib/jutils-1.0.0.jar
lib/lwjgl-2.8.2.jar
lib/lwjgl-platform-2.8.2-natives-linux.jar
lib/lwjgl-platform-2.8.2-natives-osx.jar
lib/lwjgl-platform-2.8.2-natives-windows.jar
So it appears that lwjgl has been pulled in.
What are the steps I should try to figure out which step I went wrong on?
Thanks!
Dropping this note here since google found this post for my similar question.
The Leiningen folks have now addressed this: https://github.com/technomancy/leiningen/issues/898
If you get version 2.1.0 or later, it has the fix. See the bug for details.
UPDATE: (Aug 2013)
I have a project on github I use for experimentation with lwjgl here: https://github.com/rogerallen/hello_lwjgl
I'm also using LWJGL in my shadertone project here: https://github.com/overtone/shadertone
Because Shadertone is a library, I found I needed to package up the natives myself to get it to install reasonably for projects that depend on shadertone.
If anyone has some pull with the LWJGL folks, it sure would be nice if they just put natives into appropriate subdirectories as lein expects in their clojars releases.
Looks like a problem with your LD_LIBRARY_PATH. Are you including the correct .dll or .so files?
You probably need to add something like :native-dependencies [[lwjgl "2.8.2"]] to your project.clj.
Alternatively, you could try setting the right value from your shell:
export LD_LIBRARY_PATH=/home/username/lwjgl-2.8.2/native/linux/
It's a bit confusing why Display is refusing to import, though other classes in the same jar file import properly
(import '[org.lwjgl.opengl Util WindowsAWTGLCanvasPeerInfo])
I suspect that this jar file is broken, perhaps you could try a different version.
I tried debuggin this by running
cd lib
jar xf lwjgl-2.8.2.jar
cd org/lwjgl/opengl/
and then trying to load various classes i see there.
lein swank also does tab completion which can help in exploring classes without extracting them from the shell.
Ran into this today, solved it a bit differently by adding the native directory to :jvm-opts in project.clj:
(defproject projectname "0.0.1-SNAPSHOT"
:description "my project"
:jvm-opts ["-Djava.library.path=native/linux"]
:dependencies [[org.clojure/clojure "1.4.0"]])
I copied the jar files from the latest lwjgl release into lib and copied the native directory into the project root. Seems to work so far:
user=> (import org.lwjgl.opengl.Display)
org.lwjgl.opengl.Display
But I am only just getting started. Anyway, hope this helps someone else :)
I'm new to Clojure and Leiningen, and I've determined that some of what I'll want to use is located in clojure.contrib.generic.math-functions. I found API information for that at http://richhickey.github.com/clojure-contrib/branch-1.1.x/math-api.html, but I can't find anything that helps me figure out what I should put into my project.clj file for that dependency.
I have tried [clojure.contrib.generic.math-functions "1.1"], [clojure.contrib.generic.math-functions "1.1.x"], and [clojure.contrib.generic.math-functions "1.1.0"]. For each of those, I get something like...
...
Caused by: org.apache.maven.artifact.resolver.MultipleArtifactsNotFoundException: Missing:
----------
1) clojure.contrib.generic.math-functions:clojure.contrib.generic.math-functions:jar:1.1
All clojure-contrib namespaces are shipped within a single jar file, for which the dependency has to be listed like:
[org.clojure/clojure-contrib "1.2.0"]
Please note that there are different versions available of that artifact. The 1.2.0 is the current stable release.
In order to use functions coming from the math-functions namespace in your clojure code, you need to either require or use such namespace, usually done within the ns form at the beginning of your source file:
(ns my.namespace
(:use [clojure.contrib.generic.math-functions]))
Have a look here to see the differences between use and require.
The next version of Leiningen will have a search task for precisely this purpose. It will search Clojars, Maven Central, and any other repositories your project has listed, provided they offer up downloadable indices. It's already implemented, so if you run Leiningen from git you can use it.
Also, the Leiningen tutorial covers this. Type "lein help tutorial".
You can generally find what you need at clojars.org - it's the default repository for leiningen. The current stable release of Clojure is 1.2.0, so you'd have this in your leiningen project.clj:
[org.clojure/clojure "1.2.0"]
[org.clojure/clojure-contrib "1.2.0"]
To use the generic math functions in your clojure, require or use it in your namespace declaration at the top of your source file:
(ns your-namespace
(:use [clojure.contrib.generic.math-functions :as mathf]))
This allows you to refer to the functions in that namespace like this:
(mathf/abs -10) ;; => 10
:use-ing namespaces with :as is the preferred way to use functions from other namespaces in your code. require is ok, but you'd have to prefix your functions with the entire namespace (e.g. clojure.contrib.generic.math-functions/abs) so that's not practical. Using a namespace without :as allows you to use these functions without any prefix at all (e.g. abs), but you're more likely to get namespace clashes and it might be difficult to see where functions come from, especially if you :use many libraries.
You can browse all libraries available from the default leiningen repository by checking out http://clojars.org/repo/. The structure of clojure-contrib will change when 1.3.0 is out, so you'll have to include the specific contrib library if you're using version 1.3.0-alpha-xx:
[org.clojure.contrib/generic "1.3.0-alpha4"]
Now that the clojure.contrib has been broken up, the math functions are in something called math.numeric-tower. The lein dependency is specified like this:
[org.clojure/math.numeric-tower "0.0.1"]
You can use or require as seems appropriate, for example
(use '[clojure.math.numeric-tower])