java.lang.NoClassDefFoundError: javax/json/Json
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java.lang.NoClassDefFoundError: javax/json/Json
提问by Luke Skywalker
I have a simple Java project where I would like to build a Json string. For this, I use javax.json:
我有一个简单的 Java 项目，我想在其中构建一个 Json 字符串。为此，我使用 javax.json：
import javax.json.Json;
import javax.json.JsonObjectBuilder;
public class MyClass {
public void MyFunc() {
JsonObjectBuilder myBuilder = Json.createObjectBuilder(); # this line will trigger the exception
// And some other code
}
}
The project is build with maven, and in the pom I have added these dependencies:
该项目是用 maven 构建的，在 pom 中我添加了这些依赖项：
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>javax.json</groupId>
<artifactId>javax.json-api</artifactId>
<version>1.0</version>
</dependency>
<dependency>
<groupId>org.glassfish</groupId>
<artifactId>javax.json</artifactId>
<version>1.0.4</version>
</dependency>
</dependencies>
Compilation is ok. When I execute the code using that command:
编译没问题。当我使用该命令执行代码时：
java -cp target/classes MyClass
The main is in MyClass. I get:
主要在 MyClass 中。我得到：
Exception in thread "main" java.lang.NoClassDefFoundError: javax/json/Json
[...]
Caused by: java.lang.ClassNotFoundException: javax.json.Json
at java.net.URLClassLoader.run(URLClassLoader.java:366)
at java.net.URLClassLoader.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
... 6 more
on the call to Json.createObjectBuilder().
在调用 Json.createObjectBuilder() 时。
Symptom is the same if you run it in the targer folder like that:
如果您在 targer 文件夹中运行它，则症状是相同的：
java MyClass
I have checked in my ~/.m2/repository folder and i have javax/json/javax.json-api/1.0/javax.json-api-1.0.jar. When I unzip it, I can see the Json.class file.
我已经检查了我的 ~/.m2/repository 文件夹，我有 javax/json/javax.json-api/1.0/javax.json-api-1.0.jar。当我解压它时，我可以看到 Json.class 文件。
What's wrong ???
怎么了 ？？？
采纳答案by Elad Tabak
The classpath does not have the javax.json-api-1.0.jar. Run it like this:
类路径没有 javax.json-api-1.0.jar。像这样运行它：
java -cp target/classes:~/.m2/repository/javax/json/javax.json-api/1.0/javax.json-api-1.0.jar MyClass
java -cp 目标/类：~/.m2/repository/javax/json/javax.json-api/1.0/javax.json-api-1.0.jar MyClass
回答by Marco Luzzara
Something like this just happened to me using Tomcat as container. However I am on IntelliJ and I solved it following this procedure:
像这样的事情发生在我使用 Tomcat 作为容器的时候。但是我在 IntelliJ 上，我按照以下程序解决了它：
Project Structure→ Artifacts→ (select your artifact)
项目结构→工件→（选择您的工件）
On Output Layoutyou will see Maven's Project Libraries, select those for which you get a ClassNotFoundException, open the context menu (right click) and click on Put into /WEB-INF/lib.
在输出布局上，您将看到 Maven 的项目库，选择您获得 的项目库，ClassNotFoundException打开上下文菜单（右键单击）并单击放入 /WEB-INF/lib。
Automatically Tomcat will check on WEB-INF/libafter its own libfolder if it does not find here a reference to a class.
如果 Tomcat 在这里没有找到对类的引用，它会自动检查WEB-INF/lib它自己的lib文件夹。
Sorry for the off-topic on IntelliJ but it could have helped me too.
很抱歉在 IntelliJ 上跑题了，但它也可以帮助我。
