转自: http://scala-ide.org/docs/current-user-doc/faq/index.html
What Eclipse Platforms are supported?
The Scala IDE 3.0 officially supports both&&and has experimental support for&and&.
I have a Retina Display and Eclipse looks blurry. How can I fix it?
You need to tell Mac OS that Eclipse is high-resolution capable.
Right-click on the Eclipse.app and choose &Show package contents&
Open Contents/Info.plist in an editor
Add the following at the end of the file, just before the closing tags. It should look like this:
Move the Eclipse.app to a new folder (to clear OS X&s cache of the Info.plist), then move it back to the old folder.
Launch Eclipse
What Eclipse package should I use?
The Scala IDE can be installed effortless on any of the below Eclipse packages:
Eclipse Classic / Eclipse Standard
Eclipse IDE for Java EE Developers
Eclipse IDE for Java Developers
SpringSource Tool Suite
If you are using one of the above Eclipse packages you are all set and ready to&.
In case you are using a different Eclipse package (e.g., Eclipse IDE for C/C++ Developers), don&t panic, the Scala IDE has only one dependency and it&s a two minutes job to update your Eclipse environment and be ready to start your Scala journey.
Start by installing the Eclipse JDT (Eclipse Java Development Tools). To do so, open Eclipse and go to the&Help&&&Install&New&Software&menu, select the eclipse update site (e.g. &Indigo -&) and, under the Programming Languages section, select Eclipse Java Development Tools. Install it.
Now that the JDT is installed, go ahead and&.
Can I install more than one Scala IDE plugin?
Currently, it is not possible to install more than one Scala IDE plugin within the same Eclipse installation. You need to decide what version of Scala you want to be using and then choose the appropriate update site.
I have an existing Java project and I wish to add Scala files. How do I convince Eclipse to work with Scala?
Right click on the project in the Package Explorer view, and in the context menu select&Configure&&Add&Scala&Nature.
I am running out of stack space in Eclipse. How do I increase the stack size?
If you are starting Eclipse from the command line, you can supply virtual machine arguments, including stack size, like this:
eclipse [normal arguments] -vmargs -Xss8M [more VM args]
You can also edit eclipse.ini in the Eclipse installation/application. There, lines that look like
can be replaced with something like (for an 8 megabyte stack, 700MB initial heap, 2GB maximum heap)
Scala IDE complains about &no Scala library...& or &More than one Scala library...&
The Scala IDE validates all Scala projects& classpaths to check that the Scala library has been correctly setup. It is checking two points: that the project build path contains only one Scala libraries, and that its version is compatible with the installed version of Scala IDE.
Not using m2eclipse
It needs to be fixed manually.
If the error is &no Scala library...&, one Scala library needs to be added to the build path. The simplest thing is to add the Scala library container: right-click on the project in the Package Explorer view, then in the context menu select&Build&Path&&&Add&Libraries..., and add the&Scala&Library.
If the error is &more than one Scala library...&, the number of Scala libraries needs to limited to one in the build path. If possible, make it being the Scala library container provided by Scala IDE.
Using m2eclipse
With projects imported using m2eclipse, the classpath validator can report an error because the Scala library is visible more than once in the build path. The&&project was created to, among other things, fix these classpath problems.
Use this&&to get the latest version.
After installation, re-importing your projects should get them configured correctly.
Scala IDE complains about &... is cross-compiled with an incompatible version of Scala ...&
The Scala IDE tries to check if binary incompatible Scala libraries have been inadvertently mixed in a project&s classpath. It works by extracting, from the name of the jars, which major version of Scala it has been compiled against (assuming the Scala convention for publishing cross-compiled libraries, and further assuming that Scala minor releases are binary compatible). If the extracted Scala major version doesn&t match the one bundled with the Scala IDE, a problem is reported. This ad-hoc validation prevents one of the most common reason for compiler crashes and lack of intelligent behavior in the Scala IDE.
If this check returns a false-negative, it can be disabled at the workspace level, or at the project level. The setting is&withVersionClasspathValidator&in the&Scala&&&Compiler&&&Build&Manager&preference section.
Scala Interpreter
What are the limitations?
The colon commands available in the terminal REPL are not supported.
Commands cannot be forcibly killed. For example, if an infinite loop is launched, it will continue in the background until Eclipse is shutdown.
Know Issues
Do Not Enter road sign when opening a Scala Editor
When opening a Scala editor, the error &Could not open the editor: org.eclipse.jdt.pilationUnit cannot be cast to scala.tools.eclipse.InteractiveCompilationUnit& (or something similar) appears.
The Scala IDE uses weaving to behave as (much) more than a Java editor on Scala files, and this is the message you get when it is not active.
JDT weaving is activated by default. Moreover, Scala plugin checks it is activated at every launch. The easiest way to debug this is therefore to accept activation of JDT weaving at launch. Otherwise, you can look into turning it on manually using the&.
Scala errors on all Unicode arrows
The code contains Unicode niceties like&&&and&&rA, but the editor doesn&t seem to be able to display them, and errors are reported at their location.
The operating system is not using UTF-8 by default, and its default encoding is used inside Eclipse.
The encoding used to open files can be configured at different levels. Most of the time, setting Eclipse default encoding to UTF-8 in&General&&&Workspace&in the preferences&&is enough. But in some case, the wrong encoding might also have been set in the project properties, or even the file properties.
Red screen of death (red squiggles everywhere)
The number one cause of&nothing works&is a mismatch between the Scala version of the Eclipse plug-in and your project&s. Make sure there is only one version of the Scala library on your classpath, and that it matches the version provided by Scala IDE. The prime suspect is Maven Dependencies, which can download and add an incompatible scala-library.jar.
The classpath validator added in Scala IDE 2.0.0 should detect this problem and provide meaningful problem markers.
No completions available
When pressing Ctrl-Space, the list doesn&t contain code completion proposals, only templates, but other semantic actions (such as hyperlinking) work fine.
During the development of version 2.0.0, the configuration of the Scala completion engines has been modified to make sure that no more disabled by mistake. If Scala IDE has been updated from an old beta version, it is possible that the Scala completion engines (Scala&Completions&and&Scala&Completion(Java&sources)) need to be re-enabled.
The diagnostic tool at&Scala&&&Run&Setup&Diagnostic&allows to fix this problem. Make sure that&UseScala-compatible&JDT&content&assist&proposals&is enabled.
Bad completion when using companion object in Java
Using the Java code assist to access a Scala companion object generates invalid code.
package stest
object S3 {
def some { }
package jtest;
import stest.S3;
public class J {
public void s() {
S3$.// call code assist here, select MODULE$
This a JDT problem. See&.
Eclipse freezes (deadlock)
The IDE is completely frozen.
A known manifestation of this problem occurs when the&SmartIndenter&kicks in (for instance when a return carriage is inserted in the Eclipse Editor), which is particularly annoying since all unsaved work will be lost.
Apparently, this problem is due to a bug in the Oracle JVM, and it is fixed in the JRE 7 (). Hence, you should not experience this problem if you upgrade to JRE 7 or newer.
If you cannot use the JRE 7, then you can try the workaround described below.
Workaround:
If the deadlock is an instance of&&(deadlock in the JDT weaving code) or&(deadlock during indentation) you can edit your eclipse.ini file using the recommended settings:
-XX:+UnlockDiagnosticVMOptions
-XX:+UnsyncloadClass
-Dosgi.classloader.lock=classname
This will reduce the probability of getting a deadlock, but wont fix it.
If you encounter this problem, the best thing is to take a thread dump:
Once the IDE is frozen, the following command provide the process id of the running virtual machines:
Then this command generates the thread dump:
$ jstack &pid&
If the thread dump doesn&t match the one in&&or&, please open a new ticket with your thread dump attached.
NoClassDefFoundError (scala/tools/nsc/settings/MutableSettings$SettingValue)
After upgrading the Scala plug-in,&java.lang.NoClassDefFoundError:scala/tools/nsc/settings/MutableSettings$SettingValue&exception is reported for all Scala projects in the workspace. Scala IDE is then unusable.
If you have several update sites providing different version of Scala IDE, Eclipse may have decided that a newest Scala library should be used instead of the one provided by the plug-in to be installed. To avoid this problem, make sure to uncheck the&Contact&all&update&sites&during&install&to&findrequired&software&option. It is situated at the bottom of the&Help&&&Install&New&Software...&dialog.
Incorrect compiler error reported in the Scala Editor
A compiler error is reported in the Scala editor, when indeed the code is correct.
In rare circumstances, the interactive typecheker (a.k.a., presentation compiler) can get in a state where it reports false, type-checking errors. As a workaround, we&ve provided a UI action that force restarts the presentation compiler. You can access it by right clicking on the project folder in the Package Explorer view, then&Scala&&&Restart&Presentation&Compiler. If the incorrect error is still reported after restarting the presentation compiler, please drop us a note in the scala-ide-user mailing list.
阅读(...) 评论()很多学spark的同学,很可能会选择使用Scala作为开发语言,Scala的ide有很多.
其中,我使用过Sublime Text3,感觉很轻便,只是缺少很多功能,它不像是一个ide,更像是一个升级版的notepad.
后来用过IntelliJ IDEA, 挺不错,开发功能齐全,虽然收费,不过开发Scala可以用免费版的,不过用惯了eclipse,使用IntelliJ IDEA还真是挺不习惯,好多快捷键总是按成eclipse的了.
下载Scala版eclipse
目前Scala的官网提供了Windows 64位的eclipse版ide
下载好了,解压即可使用,新建项目的后,需要注意把Scala包,改成下面这个
然后写个HelloWorld吧!
有些同学可能会遇到版本不匹配的问题
关于64位的eclipse版ide如何匹配32位的jdk
其实是不可能匹配的,但是有解决版本不匹配的办法,而且不影响以前的程序和相关软件配置,可以再装一个jdk.
一台Windows电脑是可以装多个版本的jdk的,需要注意的是,安装的文件位置不能一样.
我的电脑分别装了32位1.8的jdk,64位1.8的jdk
但是环境变量只能配置一个版本的jdk
我的电脑配置的是32位的jdk,刚下载的eclipse是64位的,怎么办?
修改eclipse的配置文件eclipse.ini
添加下面的配置
第二行的路径是安装的64位jdk的javaw.exe全路径
C:\Program Files\Java\jdk1.8.0_131\bin\javaw.exe
保存后,直接运行eclipse即可!
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12:07 by Rollen Holt, ... 阅读,
最近在完成自己的开源项目的时候，使用了Scala编程语言。
在使用了一段时间下来以后，有一些不是很“清晰”的感受，说实话我自己还没有很好的整理清楚，所以就先记录下来，不保证一定正确，只是个人的在现有经验下的看法而已
框架的选择
Java之所以这么繁荣很大的程度上是因为第三方开源社区的支持，当我们使用Java完成一些项目的时候，我往往都是先求助于开源社区，看看是否存在现有的解决方案，绝大多数时候我们都能找到合适的框架，然后直接用或者稍微修改一下就好了。
而且由于Java毕竟已经在企业开发领域活了许久了，因此很多领域中，业界往往都已经选择出了“佼佼者”，比如我们使用Spring来管理Bean的生命周期，使用Spring MVC作web框架，Mybatis作持久层的框架使用，AOP使用Spring AOP或者更强大的Aspectj等。
而由于Scala也是近几年“流行”起来的，虽然使用Scala编写的开源框架很多，但是在很多领域中，往往都还没有选择出其中的“佼佼者”，因此对于我们这些初学者来说，往往都会存在：「不知道该用什么框架」的疑惑。
虽然有 但是我们也开源发现很少有一家独大的情况。不过好在Scala基于JVM，可以使用Java的框架，这样我们的选择面也更加的多了起来。
我最初在完成Application-center的时候，调研了下面的几组方案：
Play framework + Slick 3.0.3
Spray-can + Slick
Spring MVC + Mybatis
Play Framework从目前来看在Scala编写的web框架中处于稍微“领先”的地位，但是对于之前一直使用Spring Mvc的Java开发者来说，在使用习惯上差别太大了。还有Slick，感觉这个框架是像整合hibernate和Mybatis的优良属性，但是目前感觉有点“四不像”，而且对事务的支持感觉太低级了，完成没法和Spring的事务管理器相提并论。也由很多开发者，包括我也使用Scala基于JDBC的风格编写过一个Scala JDBC小工具来和关系型数据库打交道。但是说实话都不是太好用。Spray的那一套东西，基于Akka，性能很不错，但是那套东西不是为了web开发而弄的，更多的是为了后端数据接口弄的。而且对于不熟悉Akka的开发者来说，学习成本简直不要太高太高。
项目初期我都使用新的工程尝试了前两种解决方案，可能是因为我对Scala和Akka还不是很熟练，所以感觉学习成本高了很多，尤其是Spray那玩意，让我一度怀疑我的智商。
因此为了「不折腾」为了加速开发进度，我最终还是选择了Spring Boot + Mybatis来完成开发。之所以这么选择主要还是因为没有学习成本，而且进度，可能出现的问题我都可控制。
编程语言的定位
此处建议大家看看，说的非常的好
暂时只想到了这么多，后续有更多的想法的时候，我再更新这个文章。Scala详细总结(精辟版++)_百度文库
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