Java 在读取JSON文件时遇到一些问题

我有一个JSON文件，其中包含一个字典（一个真正的英语到波斯语的字典），我编写了一个java类来读取它，但它不起作用 我写了一个函数，我用它来读取文件的特定部分

这是我的阅读课：

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import org.json.simple.JSONArray;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;

public class JSONReader {
    static JSONParser parser = new JSONParser();
    static JSONArray dictarray;
    public static void main(String[] args) throws FileNotFoundException, ParseException, IOException {
        Object obj = parser.parse(new FileReader("C:\\Users\\Mohsen\\Documents\\NetBeansProjects\\DSFP2\\dictionary.JSON"));
        JSONArray dictarray = (JSONArray)obj;
    }

    public void read() {
        System.out.println(dictarray.get(0));
    }
}

这是FXMLController文件，它创建此类的新对象并尝试使用它：

public class FXMLDocumentController implements Initializable {
    JSONReader JR = new JSONReader();

    @FXML
    private void action (KeyEvent event) {
        JR.read();
    }

    @Override
    public void initialize(URL url, ResourceBundle rb) {

    }    

}

这就是我得到的错误：

Executing C:\Users\Mohsen\Documents\NetBeansProjects\DSFP2\dist\run1082927040\DSFP2.jar using platform C:\Program Files\Java\jdk1.8.0_45\jre/bin/java
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1770)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1653)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Scene$KeyHandler.process(Scene.java:3965)
    at javafx.scene.Scene$KeyHandler.access$1800(Scene.java:3911)
    at javafx.scene.Scene.impl_processKeyEvent(Scene.java:2040)
    at javafx.scene.Scene$ScenePeerListener.keyEvent(Scene.java:2502)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$KeyEventNotification.run(GlassViewEventHandler.java:197)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$KeyEventNotification.run(GlassViewEventHandler.java:147)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleKeyEvent$349(GlassViewEventHandler.java:228)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$$Lambda$195/1857609670.get(Unknown Source)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:404)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleKeyEvent(GlassViewEventHandler.java:227)
    at com.sun.glass.ui.View.handleKeyEvent(View.java:546)
    at com.sun.glass.ui.View.notifyKey(View.java:956)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$145(WinApplication.java:101)
    at com.sun.glass.ui.win.WinApplication$$Lambda$36/1963387170.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1765)
    ... 31 more
Caused by: java.lang.NullPointerException
    at JSONReader.read(JSONReader.java:17)
    at FXMLDocumentController.action(FXMLDocumentController.java:11)
    ... 41 more

---

问题出在哪里？

您正在

JSONReader

类的

main

方法中读取文件，该方法永远不会执行，因为它不是应用程序的主类

将该代码放入

read

方法：

public class JSONReader {
    JSONArray dictarray;

    public void read()  throws FileNotFoundException, ParseException, IOException {
        JSONParser parser = new JSONParser();
        Object obj = parser.parse(new FileReader("C:\\Users\\Mohsen\\Documents\\NetBeansProjects\\DSFP2\\dictionary.JSON"));
        dictarray = (JSONArray)obj;
    }
}

编辑01.01.2020:

要只读取一次文件，请将该代码移动到一个单独的方法中-我将其命名为

init

，并调用该方法一次，您还可以将其放入构造函数中。然后在

read

方法中，您可以访问以前读取的数据

public class JSONReader {
    static JSONArray dictarray;

    public void init()  throws FileNotFoundException, ParseException, IOException {
        JSONParser parser = new JSONParser();
        Object obj = parser.parse(new FileReader("C:\\Users\\Mohsen\\Documents\\NetBeansProjects\\DSFP2\\dictionary.JSON"));
        dictarray = (JSONArray)obj;
    }

    public Object read() {
      return dictarray.get(0);
    }
}

---

但是在这个解决方案中，每次我想读取文件时，我都必须打开它！我试图以一种只有一个开头就足够的方式来写作！但无论如何，tnQ@MohsenAmiriAmjad为什么需要多个

JSONReader

类的实例？如果程序设计正确，您应该能够在需要访问的代码部分之间共享数据。如果坚持使用

static

数据（这是一种糟糕的做法），您仍然可以将文件读取移动到

static

初始值设定项块或使用单例。请注意，在实数代码中，对这样的文件路径进行硬编码是不可能的…@MohsenAmiriAmjad我更新了我的答案，并从字段中删除了静态内容，多亏了@fabian，我错过了这一点。