java - 源代码无法编译——未报告异常java.lang.Exception；必须被捕获或宣布被扔出

Question

我是 JAVA 新手，刚刚学习了它的基础知识，现在我正在尝试学习一些高级 JAVA 我不知道它是否先进，但我想做的是当我单击“搜索”按钮时我将发送 1 个 http 调用，当我删除 http 请求代码或删除搜索按钮代码时，它会单独工作，但不能一起工作

这是我的代码:

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */

package google;
import java.io.*;
import java.net.*;
import java.awt.event.*;
import javax.swing.*;
/**
 *
 * @author user
 */

public class Google extends JFrame {

    private final String USER_AGENT = "Mozilla/5.0";

    public Google() {
       initUI();
    }

    private void callUrl() throws Exception {

        String url = "http://www.google.com/search?q=mkyong";

        URL obj = new URL(url);
        HttpURLConnection con = (HttpURLConnection) obj.openConnection();

        // optional default is GET
        con.setRequestMethod("GET");

        //add request header
        con.setRequestProperty("User-Agent", USER_AGENT);

        int responseCode = con.getResponseCode();
        System.out.println("\nSending 'GET' request to URL : " + url);
        System.out.println("Response Code : " + responseCode);

        BufferedReader in = new BufferedReader(
                new InputStreamReader(con.getInputStream()));
        String inputLine;
        StringBuffer response = new StringBuffer();

        while ((inputLine = in.readLine()) != null) {
            response.append(inputLine);
        }
        in.close();

        //print result
        System.out.println(response.toString());

    }

    private void initUI() {

       JPanel panel = new JPanel();
       getContentPane().add(panel);

       panel.setLayout(null);

       JButton searchButton = new JButton("Search");
       searchButton.setBounds(50, 60, 80, 30);

       searchButton.addActionListener(new ActionListener() {
           @Override
           public void actionPerformed(ActionEvent event)  {
               callUrl();
          }
       });

       panel.add(searchButton);

       setTitle("Search");
       setSize(300, 200);
       setLocationRelativeTo(null);
       setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    public static void main(String[] args) throws Exception {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                Google ex = new Google();
                ex.setVisible(true);
            }
        });
    }

}

抱歉，如果这个问题已经存在，我进行了很多搜索，但没有得到正确的解决方案。谢谢

错误:

Exception in thread "AWT-EventQueue-0" java.lang.RuntimeException: Uncompilable source code - unreported exception java.lang.Exception; must be caught or declared to be thrown
    at google.Google$1.actionPerformed(Google.java:70)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6505)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
    at java.awt.Component.processEvent(Component.java:6270)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
    at java.awt.EventQueue.access$200(EventQueue.java:103)
    at java.awt.EventQueue$3.run(EventQueue.java:694)
    at java.awt.EventQueue$3.run(EventQueue.java:692)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:708)
    at java.awt.EventQueue$4.run(EventQueue.java:706)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

Answer 1

这并不完全针对您的问题，但它将帮助您了解 java 中的异常处理。

有两种类型的异常

• 检查异常
• 未经检查的异常

检查的异常应该在代码中处理，这意味着您要么需要在方法中处理，要么抛出异常，以便方法的调用者处理。

要捕获异常，您需要使用try和catch。如果您不想处理异常，可以将您的方法声明为 throws SomeException 以便调用者能够处理。

例如:

public String getContentsOfFile(String filePath) {
    try {
        File file = new File(filePath);
        FileInputStream fis = new FileInputStream(file);   
        String contents = //convert stream to string and return
        return contents;
    } catch(FileNotFoundException e){
        //Here this method is interested in handling the checked exception.
    } 
    return null;
}

如果你不想处理异常(你让你的方法抛出异常)

public String getContentsOfFile(String filePath) throws FileNotFoundException {

    File file = new File(filePath);
    FileInputStream fis = new FileInputStream(file);   
    String contents = //convert stream to string and return
    return contents;        
}

另一个最佳实践是，您可以捕获已检查的异常并抛出未检查的异常 (RuntimeException)，以便方法的调用者不需要处理该异常。 Spring 广泛使用这种方法。

try {
.....
} catch (FileNotFoundException fne) {
    //log fne
    throw new RuntimeException(fne);
}

这里有一个关于何时选择 Checked 异常以及何时选择 Unchecked 异常的问题。 When to choose checked and unchecked exceptions