Java Gradle - 无法找到或加载主类
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Gradle - Could not find or load main class
提问by twilco
I'm trying to run a very simple project using Gradle and running into the following error when using the gradlew run command:
我正在尝试使用 Gradle 运行一个非常简单的项目，并在使用时遇到以下错误gradlew run command：
could not find or load main class 'hello.HelloWorld'
could not find or load main class 'hello.HelloWorld'
Here is my file structure:
这是我的文件结构：
SpringTest
-src
-hello
-HelloWorld.java
-Greeter.java
-build
-libs
-tmp
-gradle
-wrapper
-build.gradle
-gradlew
-gradlew.bat
I excluded the contents of the libs and tmp folders because I didn't think that would be relevant information for this issue, but I can add it in if need be.
我排除了 libs 和 tmp 文件夹的内容，因为我认为这不是此问题的相关信息，但如果需要，我可以将其添加。
Here is my build.gradle file:
这是我的 build.gradle 文件：
apply plugin: 'java'
apply plugin: 'application'
apply plugin: 'eclipse'
mainClassName = 'hello/HelloWorld'
repositories {
mavenLocal()
mavenCentral()
}
dependencies {
compile "joda-time:joda-time:2.2"
}
jar {
baseName = "gs-gradle"
version = "0.1.0"
}
task wrapper(type: Wrapper) {
gradleVersion = '1.11'
}
Any idea on how to fix this issue? I've tried all sorts of things for the mainClassName attribute but nothing seems to work.
关于如何解决这个问题的任何想法？我已经为 mainClassName 属性尝试了各种方法，但似乎没有任何效果。
采纳答案by kdabir
I see two problems here, one with sourceSetanother with mainClassName.
我在这里看到两个问题，一个sourceSet是mainClassName.
Either move java source files to
src/main/javainstead of justsrc. Or setsourceSetproperly by adding the following to build.gradle.sourceSets.main.java.srcDirs = ['src']mainClassNameshould be fully qualified class name, not path.mainClassName = "hello.HelloWorld"
上移java源文件
src/main/java，而不是只src。或者sourceSet通过将以下内容添加到 build.gradle 来正确设置。sourceSets.main.java.srcDirs = ['src']mainClassName应该是完全限定的类名，而不是路径。mainClassName = "hello.HelloWorld"
回答by hepifish
I just ran into this problem and decided to debug it myself since i couldn't find a solution on the internet. All i did is change the mainClassName to it's whole path(with the correct subdirectories in the project ofc)
我刚遇到这个问题并决定自己调试它，因为我在互联网上找不到解决方案。我所做的就是将 mainClassName 更改为它的整个路径（在项目 ofc 中使用正确的子目录）
mainClassName = 'main.java.hello.HelloWorld'
I know it's been almost one year since the post has been made, but i think someone will find this information useful.
我知道帖子发布已经快一年了，但我认为有人会发现这些信息很有用。
Happy coding.
快乐编码。
回答by Noumenon
Modify build.gradle to put your main class in the manifest:
修改 build.gradle 将您的主类放在清单中：
jar {
manifest {
attributes 'Implementation-Title': 'Gradle Quickstart',
'Implementation-Version': version,
'Main-Class': 'hello.helloWorld'
}
}
回答by Dino Tw
Struggled with the same problem for some time. But after creating the directory structure src/main/java and putting the source(from the top of the package), it worked as expected.
为同样的问题苦苦挣扎了一段时间。但是在创建目录结构 src/main/java 并放置源代码（从包的顶部）之后，它按预期工作。
The tutorialI tried with. After you execute gradle build, you will have to be able to find classesunder builddirectory.
我试过的教程。执行后gradle build，您必须能够classes在build目录下找到。
回答by Psi-Ed
In my build.gradle, I resolved this issue by creating a task and then specifying the "mainClassName" as follows:
在我的 build.gradle 中，我通过创建一个任务然后指定“mainClassName”来解决这个问题，如下所示：
task(runSimpleXYZProgram, group: 'algorithms', description: 'Description of what your program does', dependsOn: 'classes', type: JavaExec) {
mainClassName = 'your.entire.package.classContainingYourMainMethod'
}
回答by Nav
Just to make it clear for newbies trying to run a gradle project from Netbeans:
To understand this, you need to see what the main class name looks like andwhat the gradle build looks like:
只是为了让尝试从 Netbeans 运行 gradle 项目的新手清楚：
要理解这一点，您需要查看主类名称的外观以及gradle 构建的外观：
Main class:
主要类：
package com.stormtrident;
public class StormTrident {
public static void main(String[] cmdArgs) {
}
}
Notice that it is part of the package "com.stormtrident".
请注意，它是“com.stormtrident”包的一部分。
Gradle build:
摇篮构建：
apply plugin: 'java'
defaultTasks 'jar'
jar {
from {
(configurations.runtime).collect {
it.isDirectory() ? it : zipTree(it)
}
}
manifest {
attributes 'Main-Class': 'com.stormtrident.StormTrident'
}
}
sourceCompatibility = '1.8'
[compileJava, compileTestJava]*.options*.encoding = 'UTF-8'
if (!hasProperty('mainClass')) {
ext.mainClass = 'com.stormtrident.StormTrident'
}
repositories {
mavenCentral()
}
dependencies {
//---apache storm
compile 'org.apache.storm:storm-core:1.0.0' //compile
testCompile group: 'junit', name: 'junit', version: '4.10'
}
回答by JohnTheBeloved
I fixed this by running a clean of by gradle build (or delete the gradle build folder mannually)
我通过运行清理 by gradle build（或手动删除 gradle build 文件夹）解决了这个问题
This occurs if you move the main class to a new package and the old main class is still referenced in the claspath
如果您将主类移动到新包并且在 claspath 中仍然引用旧的主类，则会发生这种情况
回答by RichArt
When I had this error, it was because I didn't have my class in a package. Put your HelloWorld.javafile in a "package" folder. You may have to create a new package folder:
当我遇到这个错误时，是因为我的类没有放在 package 中。将您的HelloWorld.java文件放在“包”文件夹中。您可能需要创建一个新的包文件夹：
Right click on the hellofolder and select "New" > "Package". Then give it a name (e.g: com.example) and move your HelloWorld.javaclass into the package.
右键单击hello文件夹并选择“新建”>“包”。然后给它一个名字（例如：com.example）并将你的HelloWorld.java类移动到包中。
回答by cane
verify if gradle.propertiesdefine right one JAVA_HOVE
org.gradle.java.home=C:\Program Files (x86)\Java\jdk1.8.0_181
验证gradle.properties是否定义了正确的 JAVA_HOVE
org.gradle.java.home=C:\Program Files (x86)\Java\jdk1.8.0_181
or
或者
- if it's not defined be sure if Eclipse know JDK and not JRE
- 如果未定义，请确定 Eclipse 是否知道 JDK 而不是 JRE
回答by Premakumar
I resolved it by adding below code to my application.
我通过将以下代码添加到我的应用程序来解决它。
// enter code here this is error I was getting when I run build.gradle. main class name has not been configured and it could not be resolved
// 在此处输入代码 这是我运行 build.gradle 时遇到的错误。主类名未配置，无法解析
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
