java—尝试创建javafx应用程序，允许用户轻松地监视和维护嵌入式derby数据库中的网站列表

我想让用户拖放一个链接到列表，这将进入数据库的网址，允许用户查看所有的链接，文章，或类似的东西在页面的右上角（即使是简单的细节，如标题和链接是什么时候被添加的罚款），然后查看网页视图。我无法让它在右上角正确显示url详细信息，或在右下角正确显示webview。我对javafx和derby非常熟悉，只是对web方面不太熟悉。任何帮助都将不胜感激。到目前为止，url可以拖放到列表中，标题和一些详细信息在右上角显示不正确。webview在大多数情况下也不起作用。超链接也无法在列表中正确显示，但这只是一些需要修复的格式。最终目标只是允许用户在他们输入的url上监视新的帖子、文章或新闻。

DBUtils.java

public class DBUtils {
    final static Properties props = new Properties(); 
    static {
        props.put("user", "admin");
        props.put("password", "letmein");
    }
    private static String framework = "embedded";
    private static String driver = "org.apache.derby.jdbc.EmbeddedDriver";
    private static String protocol = "jdbc:derby:";
    public static void setupDb() {
        loadDriver();
        Connection conn = null;
        ArrayList statements = new ArrayList(); 
        Statement s = null;
        ResultSet rs = null;
        try {
            String dbName = "UrlDB"; 
            conn = DriverManager.getConnection(protocol + dbName + ";create=true", props);
            System.out.println("Creating database " + dbName);
            boolean createTable = false;
            s = conn.createStatement();
            try {
                s.executeQuery("SELECT count(*) FROM urlFeed");
            } catch (Exception e) {
                createTable = true;
            }     
            if (createTable) {
                conn.setAutoCommit(false);
                s = conn.createStatement();
                statements.add(s);
                s.execute("CREATE TABLE UrlFeed(ID INT, Title VARCHAR(255), Url VARCHAR(600))");
                System.out.println("Created table UrlFeed ");
                conn.commit();
            }         
            shutdown();
        } catch (SQLException sqle) {
            sqle.printStackTrace();
        } finally {         
            close(rs);
            int i = 0;
            while (!statements.isEmpty()) {
                Statement st = (Statement) statements.remove(i);
                close(st);
            }
            close(conn);
        }} 
    public static List<UrlFeed> loadFeeds() {
        loadDriver();
        Connection conn = null;
        ResultSet rs = null;
        List<UrlFeed> feeds = new ArrayList<>();
        try {
            String dbName = "UrlDB"; 
            conn = DriverManager.getConnection(protocol + dbName + ";create=true", props);
            rs = conn.createStatement().executeQuery("SELECT ID, Title, Url FROM UrlFeed");
            while (rs.next()) {
                String title = rs.getString("title");
                String url = rs.getString("url");
                UrlFeed urlFeed = new UrlFeed(title, url);
                urlFeed.id = urlFeed.link.hashCode();
                feeds.add(urlFeed);
            } 
            shutdown();
        } catch (SQLException sqle) {
            sqle.printStackTrace();
        } finally {         
            close(rs);
            close(conn);
        }
        return feeds;
    }
    private static void shutdown() {
        if (framework.equals("embedded")) {
            try {
                DriverManager.getConnection("jdbc:derby:;shutdown=true");
            } catch (SQLException se) {
                if (((se.getErrorCode() == 50000)
                        && ("XJ015".equals(se.getSQLState())))) {
                    System.out.println("Derby shut down normally");
                } else {
                    System.err.println("Derby did not shut down normally");
                    se.printStackTrace();
                }}
        }}  
    public static int saveUrlFeed(UrlFeed urlFeed) {
        int pk = urlFeed.link.hashCode();
        loadDriver();
        Connection conn = null;
        ArrayList statements = new ArrayList(); 
        PreparedStatement psInsert = null;
        Statement s = null;
        ResultSet rs = null;
        try {
            String dbName = "UrlDB"; 
            conn = DriverManager.getConnection(protocol + dbName + ";create=true", props);
            rs = conn.createStatement().executeQuery("SELECT COUNT(id) FROM UrlFeed WHERE id = " + urlFeed.link.hashCode());           
            rs.next();
            int count = rs.getInt(1);           
            if (count == 0) {
                conn.setAutoCommit(false);
                s = conn.createStatement();
                statements.add(s);
                psInsert = conn.prepareStatement("INSERT INTO UrlFeed VALUES (?, ?, ?)");
                statements.add(psInsert);
                psInsert.setInt(1, pk);
                String escapeTitle = urlFeed.channelTitle.replaceAll("\'", "''");
                psInsert.setString(2, escapeTitle);
                psInsert.setString(3, urlFeed.link);
                psInsert.executeUpdate();
                conn.commit();
                System.out.println("Inserted " + urlFeed.channelTitle + " " + urlFeed.link);
                System.out.println("Committed the transaction");
            }
            shutdown();
        } catch (SQLException sqle) {
            sqle.printStackTrace();
        } finally {
            close(rs);
            int i = 0;
            while (!statements.isEmpty()) {
                Statement st = (Statement) statements.remove(i);
                close(st);
            }
            close(conn);
        }
        return pk;
    }
    private static void close(AutoCloseable closable) {
        try {
            if (closable != null) {
                closable.close();
                closable = null;
            }
        } catch (Exception sqle) {
            sqle.printStackTrace();
        }
    }
    private static void loadDriver() {     
            try {
                Class.forName(driver);
                System.out.println("Loaded driver");           
            } catch (Exception e) {
                e.printStackTrace();
            }    
    }
}

DisplayContentsFromDatabase.java

public class DisplayContentsFromDatabase extends Application {
    @Override public void start(Stage stage) {
        Group root = new Group();
        Scene scene = new Scene(root, 640, 480, Color.WHITE);
        final Map<String, Hyperlink> hyperLinksMap = new TreeMap<>();      
        final WebView newsBrief = new WebView(); 
        final WebEngine webEngine = new WebEngine();
        final WebView websiteView = new WebView();      
        webEngine.getLoadWorker().stateProperty().addListener(new ChangeListener<State>() {
            public void changed(ObservableValue<? extends State> observable, State oldValue, State newValue){
                if (newValue != State.SUCCEEDED) {
                    return;
                }               
                UrlFeed urlFeed = parse(webEngine.getDocument(), webEngine.getLocation());
                hyperLinksMap.get(webEngine.getLocation()).setText(urlFeed.channelTitle);               
                StringBuilder urlSource = new StringBuilder();
                urlSource.append("<head>\n")
                         .append("</head>\n")
                         .append("<body>\n");
                urlSource.append("<b>")
                         .append(urlFeed.channelTitle)
                         .append(" (")
                         .append(urlFeed.news.size())
                         .append(")")
                         .append("</b><br />\n");
                 StringBuilder htmlArticleSb = new StringBuilder();
                for (NewsArticle article:urlFeed.news) {                   
                    htmlArticleSb.append("<hr />\n")
                         .append("<b>\n")
                         .append(article.title)
                         .append("</b><br />")
                         .append(article.pubDate)
                         .append("<br />")
                         .append(article.description)
                         .append("<br />\n")
                         .append("<input type=\"button\" onclick=\"alert('")
                            .append(article.link)
                            .append("')\" value=\"View\" />\n");
                }
                String content = urlSource.toString() + "<form>\n" + htmlArticleSb.toString() + "</form></body>\n";
                System.out.println(content);
                newsBrief.getEngine().loadContent(content);
                DBUtils.saveUrlFeed(urlFeed);
            }
        }); 
        newsBrief.getEngine().setOnAlert(new EventHandler<WebEvent<String>>(){
            public void handle(WebEvent<String> evt) {
                websiteView.getEngine().load(evt.getData());
            }
        });        
        SplitPane splitPane = new SplitPane();
        splitPane.prefWidthProperty().bind(scene.widthProperty());
        splitPane.prefHeightProperty().bind(scene.heightProperty());
        final VBox leftArea = new VBox(10);
        final TextField urlField = new TextField();
        urlField.setOnAction(new EventHandler<ActionEvent>(){
            public void handle(ActionEvent ae){
                String url = urlField.getText();
                final Hyperlink jfxHyperLink = createHyperLink(url, webEngine);
                hyperLinksMap.put(url, jfxHyperLink);
                HBox rowBox = new HBox(20);
                rowBox.getChildren().add(jfxHyperLink);
                leftArea.getChildren().add(rowBox);
                webEngine.load(url);
                urlField.setText("");
            }
        });     
        leftArea.getChildren().add(urlField);        
        List<UrlFeed> urlFeeds = DBUtils.loadFeeds();
        for (UrlFeed feed:urlFeeds) {
            HBox rowBox = new HBox(20);
            final Hyperlink jfxHyperLink = new Hyperlink(feed.channelTitle);
            jfxHyperLink.setUserData(feed);
            final String location = feed.link;
            hyperLinksMap.put(feed.link, jfxHyperLink);
            jfxHyperLink.setOnAction(new EventHandler<ActionEvent>() {
                    public void handle(ActionEvent evt) {
                        webEngine.load(location);
                    }
                }
            );
            rowBox.getChildren().add(jfxHyperLink);
            leftArea.getChildren().add(rowBox);            
        }                 
        scene.setOnDragOver(new EventHandler<DragEvent>() {
            @Override
            public void handle(DragEvent event) {
                Dragboard db = event.getDragboard();
                if (db.hasUrl()) {
                    event.acceptTransferModes(TransferMode.COPY);
                } else {
                    event.consume();
                }
            }
        }); 
        scene.setOnDragDropped(new EventHandler<DragEvent>() {
            @Override
            public void handle(DragEvent event) {
                Dragboard db = event.getDragboard();
                boolean success = false;
                HBox rowBox = new HBox(20);
                if (db.hasUrl()) {
                    if (!hyperLinksMap.containsKey(db.getUrl())) {                        
                        final Hyperlink jfxHyperLink = createHyperLink(db.getUrl(), webEngine);
                        hyperLinksMap.put(db.getUrl(), jfxHyperLink);
                        rowBox.getChildren().add(jfxHyperLink);
                        leftArea.getChildren().add(rowBox);
                    }
                    webEngine.load(db.getUrl());
                }    
                event.setDropCompleted(success);
                event.consume();
            }
        });        
        leftArea.setAlignment(Pos.TOP_LEFT);        
        SplitPane splitPane2 = new SplitPane();
        splitPane2.setOrientation(Orientation.VERTICAL);
        splitPane2.prefWidthProperty().bind(scene.widthProperty());
        splitPane2.prefHeightProperty().bind(scene.heightProperty());
        HBox centerArea = new HBox();     
        centerArea.getChildren().add(newsBrief);
        HBox rightArea = new HBox();
        rightArea.getChildren().add(websiteView);
        splitPane2.getItems().add(centerArea);
        splitPane2.getItems().add(rightArea);
        splitPane.getItems().add(leftArea);
        splitPane.getItems().add(splitPane2);
        newsBrief.prefWidthProperty().bind(scene.widthProperty());
        websiteView.prefWidthProperty().bind(scene.widthProperty());
        ObservableList<SplitPane.Divider> dividers = splitPane.getDividers();
        for (int i = 0; i < dividers.size(); i++) {
            dividers.get(i).setPosition((i + 1.0) / 3);
        }
        HBox hbox = new HBox();
        hbox.getChildren().add(splitPane);
        root.getChildren().add(hbox);       
        stage.setScene(scene);
        stage.show();       
    }
    private static UrlFeed parse(Document doc, String location) {        
        UrlFeed urlFeed = new UrlFeed();
        urlFeed.link = location;        
        urlFeed.channelTitle = doc.getElementsByTagName("title")
             .item(0)
             .getTextContent();
        NodeList items = doc.getElementsByTagName("item");
        for (int i=0; i<items.getLength(); i++){
            Map<String, String> childElements = new HashMap<>();
            NewsArticle article = new NewsArticle();
            for (int j=0; j<items.item(i).getChildNodes().getLength(); j++) {
                Node node = items.item(i).getChildNodes().item(j);
                childElements.put(node.getNodeName().toLowerCase(), node.getTextContent());
            }
            article.title = childElements.get("title");
            article.description = childElements.get("description");
            article.link = childElements.get("link");
            article.pubDate = childElements.get("pubdate");           
            urlFeed.news.add(article);
        }
        return urlFeed;
    }  
    private Hyperlink createHyperLink(String url, final WebEngine webEngine) {
        final Hyperlink jfxHyperLink = new Hyperlink("Loading News...");
        UrlFeed aFeed = new UrlFeed();
        aFeed.link = url;
        jfxHyperLink.setUserData(aFeed);
        jfxHyperLink.setOnAction(new EventHandler<ActionEvent>() {
            public void handle(ActionEvent evt) {
                UrlFeed urlFeed = (UrlFeed)jfxHyperLink.getUserData();
                webEngine.load(urlFeed.link);
            }
        });
        return jfxHyperLink;
    } 
    public static void main(String[] args){
        DBUtils.setupDb();
        Application.launch(args);
    }
}
class UrlFeed {
    int id;
    String channelTitle = "News...";
    String link;
    List<NewsArticle> news = new ArrayList<>();

    public String toString() {
        return "urlFeed{" + "id=" + id + ", channelTitle=" + channelTitle + ", link=" + link + ", news=" + news + '}';
    }
    public UrlFeed() {
    }
    public UrlFeed(String title, String link) {
        this.channelTitle = title;
        this.link = link;
    }
}
class NewsArticle {
    String title;
    String description;
    String link;
    String pubDate;
    public String toString() {
        return "NewsArticle{" + "title=" + title + ", description=" + description + ", link=" + link + ", pubDate=" + pubDate + ", enclosure=" + '}';
    }  
}

我复制了你的代码并重构了它。
捕捉异常并只打印堆栈跟踪意味着程序将继续运行。例如，如果您不能加载jdbc驱动程序，那么继续下去又有什么意义呢？整个程序取决于能否与数据库交互。
无法从中恢复的异常将导致程序终止。异常可能超出您的控制范围，也可能表示程序中存在错误。
但是请注意，可以忽略这一点 SQLException 当你无法关闭 Statement 或者 ResultSet 因为即使 ResultSet / Statement 没有关闭。
您的jdbc代码应该使用try with资源。
可以使用java.sql.databasemetadata类检查表是否存在。
只需加载一次jdbc驱动程序类。
您应该只在程序终止时关闭数据库。
尽管 WebEngine 将成功加载您在 urlField ，方法返回的值 getLocation() 可能与您输入的内容不同，因此 hyperLinksMap 将不包含您搜索的密钥。因此 hyperLinksMap.get(webEngine.getLocation()) 将返回null，这意味着下面的代码行将抛出 NullPointerException .

hyperLinksMap.get(webEngine.getLocation()).setText(urlFeed.channelTitle);

你还应该处理 WebEngine 无法加载用户输入的url。
下面是重构后的代码。注意，所有的课程都是我做的 public 班级。
班级 DisplayContentsFromDatabase ```
import java.sql.SQLException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;

import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.collections.ObservableList;
import javafx.concurrent.Worker;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Orientation;
import javafx.geometry.Pos;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.Hyperlink;
import javafx.scene.control.SplitPane;
import javafx.scene.control.TextField;
import javafx.scene.input.DragEvent;
import javafx.scene.input.Dragboard;
import javafx.scene.input.TransferMode;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.scene.web.WebEngine;
import javafx.scene.web.WebEvent;
import javafx.scene.web.WebView;
import javafx.stage.Stage;

public class DisplayContentsFromDatabase extends Application {

@Override
public void start(Stage stage) throws Exception {
    Group root = new Group();
    Scene scene = new Scene(root, 640, 480, Color.WHITE);
    final Map<String, Hyperlink> hyperLinksMap = new TreeMap<>();
    final WebView newsBrief = new WebView();
    final WebEngine webEngine = new WebEngine();
    final WebView websiteView = new WebView();
    webEngine.getLoadWorker().stateProperty().addListener(new ChangeListener<Worker.State>() {
        public void changed(ObservableValue<? extends Worker.State> observable,
                            Worker.State oldValue,
                            Worker.State newValue) {
            if (newValue != Worker.State.SUCCEEDED) {
                System.out.println("Worker.State = " + newValue);
                if (newValue == Worker.State.FAILED) {
                    System.out.println("Failed to load URL.");
                }
                return;
            }
            UrlFeed urlFeed = parse(webEngine.getDocument(), webEngine.getLocation());
            String location = webEngine.getLocation();
            System.out.println("Web location: " + location);
            Hyperlink link = hyperLinksMap.get(location);
            if (link == null) {
                System.out.println("Web location mismatch.");
                return;
            }
            link.setText(urlFeed.channelTitle);
            StringBuilder urlSource = new StringBuilder();
            urlSource.append("<head>\n").append("</head>\n").append("<body>\n");
            urlSource.append("<b>").append(urlFeed.channelTitle).append(" (")
                    .append(urlFeed.news.size()).append(")").append("</b><br />\n");
            StringBuilder htmlArticleSb = new StringBuilder();
            for (NewsArticle article : urlFeed.news) {
                htmlArticleSb.append("<hr />\n").append("<b>\n").append(article.title)
                        .append("</b><br />").append(article.pubDate).append("<br />")
                        .append(article.description).append("<br />\n")
                        .append("<input type=\"button\" onclick=\"alert('").append(article.link)
                        .append("')\" value=\"View\" />\n");
            }
            String content = urlSource.toString() + "<form>\n" + htmlArticleSb.toString()
                    + "</form></body>\n";
            System.out.println(content);
            newsBrief.getEngine().loadContent(content);
            try {
                DBUtils.saveUrlFeed(urlFeed);
            }
            catch (ClassNotFoundException | SQLException x) {
                throw new RuntimeException(x);
            }
        }
    });
    newsBrief.getEngine().setOnAlert(new EventHandler<WebEvent<String>>() {
        public void handle(WebEvent<String> evt) {
            websiteView.getEngine().load(evt.getData());
        }
    });
    SplitPane splitPane = new SplitPane();
    splitPane.prefWidthProperty().bind(scene.widthProperty());
    splitPane.prefHeightProperty().bind(scene.heightProperty());
    final VBox leftArea = new VBox(10);
    final TextField urlField = new TextField();
    urlField.setOnAction(new EventHandler<ActionEvent>() {
        public void handle(ActionEvent ae) {
            String url = urlField.getText();
            final Hyperlink jfxHyperLink = createHyperLink(url, webEngine);
            hyperLinksMap.put(url, jfxHyperLink);
            HBox rowBox = new HBox(20);
            rowBox.getChildren().add(jfxHyperLink);
            leftArea.getChildren().add(rowBox);
            webEngine.load(url);
            urlField.setText("");
        }
    });
    leftArea.getChildren().add(urlField);
    List<UrlFeed> urlFeeds = DBUtils.loadFeeds();
    for (UrlFeed feed : urlFeeds) {
        HBox rowBox = new HBox(20);
        final Hyperlink jfxHyperLink = new Hyperlink(feed.channelTitle);
        jfxHyperLink.setUserData(feed);
        final String location = feed.link;
        hyperLinksMap.put(feed.link, jfxHyperLink);
        jfxHyperLink.setOnAction(new EventHandler<ActionEvent>() {
            public void handle(ActionEvent evt) {
                webEngine.load(location);
            }
        });
        rowBox.getChildren().add(jfxHyperLink);
        leftArea.getChildren().add(rowBox);
    }
    scene.setOnDragOver(new EventHandler<DragEvent>() {
        @Override
        public void handle(DragEvent event) {
            Dragboard db = event.getDragboard();
            if (db.hasUrl()) {
                event.acceptTransferModes(TransferMode.COPY);
            }
            else {
                event.consume();
            }
        }
    });
    scene.setOnDragDropped(new EventHandler<DragEvent>() {
        @Override
        public void handle(DragEvent event) {
            Dragboard db = event.getDragboard();
            boolean success = false;
            HBox rowBox = new HBox(20);
            if (db.hasUrl()) {
                if (!hyperLinksMap.containsKey(db.getUrl())) {
                    final Hyperlink jfxHyperLink = createHyperLink(db.getUrl(), webEngine);
                    hyperLinksMap.put(db.getUrl(), jfxHyperLink);
                    rowBox.getChildren().add(jfxHyperLink);
                    leftArea.getChildren().add(rowBox);
                }
                webEngine.load(db.getUrl());
            }
            event.setDropCompleted(success);
            event.consume();
        }
    });
    leftArea.setAlignment(Pos.TOP_LEFT);
    SplitPane splitPane2 = new SplitPane();
    splitPane2.setOrientation(Orientation.VERTICAL);
    splitPane2.prefWidthProperty().bind(scene.widthProperty());
    splitPane2.prefHeightProperty().bind(scene.heightProperty());
    HBox centerArea = new HBox();
    centerArea.getChildren().add(newsBrief);
    HBox rightArea = new HBox();
    rightArea.getChildren().add(websiteView);
    splitPane2.getItems().add(centerArea);
    splitPane2.getItems().add(rightArea);
    splitPane.getItems().add(leftArea);
    splitPane.getItems().add(splitPane2);
    newsBrief.prefWidthProperty().bind(scene.widthProperty());
    websiteView.prefWidthProperty().bind(scene.widthProperty());
    ObservableList<SplitPane.Divider> dividers = splitPane.getDividers();
    for (int i = 0; i < dividers.size(); i++) { dividers.get(i).setPosition((i + 1.0) / 3); }
    HBox hbox = new HBox();
    hbox.getChildren().add(splitPane);
    root.getChildren().add(hbox);
    stage.setScene(scene);
    stage.show();
}

public void stop() throws Exception {
    DBUtils.shutdown();
}

private static UrlFeed parse(Document doc, String location) {
    UrlFeed urlFeed = new UrlFeed();
    urlFeed.link = location;
    urlFeed.channelTitle = doc.getElementsByTagName("title").item(0).getTextContent();
    NodeList items = doc.getElementsByTagName("item");
    for (int i = 0; i < items.getLength(); i++) {
        Map<String, String> childElements = new HashMap<>();
        NewsArticle article = new NewsArticle();
        for (int j = 0; j < items.item(i).getChildNodes().getLength(); j++) {
            Node node = items.item(i).getChildNodes().item(j);
            childElements.put(node.getNodeName().toLowerCase(), node.getTextContent());
        }
        article.title = childElements.get("title");
        article.description = childElements.get("description");
        article.link = childElements.get("link");
        article.pubDate = childElements.get("pubdate");
        urlFeed.news.add(article);
    }
    return urlFeed;
}

private Hyperlink createHyperLink(String url, final WebEngine webEngine) {
    final Hyperlink jfxHyperLink = new Hyperlink("Loading News...");
    UrlFeed aFeed = new UrlFeed();
    aFeed.link = url;
    jfxHyperLink.setUserData(aFeed);
    jfxHyperLink.setOnAction(new EventHandler<ActionEvent>() {
        public void handle(ActionEvent evt) {
            UrlFeed urlFeed = (UrlFeed) jfxHyperLink.getUserData();
            webEngine.load(urlFeed.link);
        }
    });
    return jfxHyperLink;
}

public static void main(String[] args) {
    try {
        DBUtils.setupDb();
        Application.launch(args);
    }
    catch (Exception x) {
        x.printStackTrace();
    }
}

}

班级 `DBUtil` ```
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

public class DBUtils {
    final static Properties props = new Properties();
    static {
        props.put("user", "admin");
        props.put("password", "letmein");
    }
    private static boolean  loaded;
    private static String framework = "embedded";
    private static String driver = "org.apache.derby.jdbc.EmbeddedDriver";
    private static String protocol = "jdbc:derby:";

    public static void setupDb() throws ClassNotFoundException, SQLException {
        loadDriver();
        Statement s = null;
        ResultSet rs = null;
        String dbName = "UrlDB";
        try (Connection conn = DriverManager.getConnection(protocol + dbName + ";create=true",
                                                           props)) {
            System.out.println("Creating database " + dbName);
            DatabaseMetaData dbmd = conn.getMetaData();
            rs = dbmd.getTables(null, null, "URLFEED", null);
            boolean createTable = !rs.next();
            if (createTable) {
                s = conn.createStatement();
                s.execute("CREATE TABLE UrlFeed(ID INT, Title VARCHAR(255), Url VARCHAR(600))");
                System.out.println("Created database table 'UrlFeed'.");
            }
            else {
                System.out.println("Database table 'UrlFeed' already exists.");
            }
        }
        finally {
            if (rs != null) {
                try {
                    rs.close();
                }
                catch (SQLException xSql) {
                    // Ignore.
                }
            }
            if (s != null) {
                try {
                    s.close();
                }
                catch (SQLException xSql) {
                    // Ignore.
                }
            }
        }
    }

    public static List<UrlFeed> loadFeeds() throws ClassNotFoundException, SQLException {
        loadDriver();
        List<UrlFeed> feeds = new ArrayList<>();
        String dbName = "UrlDB";
        try (Connection conn = DriverManager.getConnection(protocol + dbName + ";create=true",
                                                           props);
             Statement s = conn.createStatement();
             ResultSet rs = s.executeQuery("SELECT ID, Title, Url FROM UrlFeed")) {
            while (rs.next()) {
                String title = rs.getString("title");
                String url = rs.getString("url");
                UrlFeed urlFeed = new UrlFeed(title, url);
                urlFeed.id = urlFeed.link.hashCode();
                feeds.add(urlFeed);
            }
        }
        return feeds;
    }

    public static void shutdown() {
        if (framework.equals("embedded")) {
            try {
                DriverManager.getConnection("jdbc:derby:;shutdown=true");
            }
            catch (SQLException se) {
                if (((se.getErrorCode() == 50000) && ("XJ015".equals(se.getSQLState())))) {
                    System.out.println("Derby shut down normally");
                }
                else {
                    System.err.println("Derby did not shut down normally");
                    se.printStackTrace();
                }
            }
        }
    }

    public static int saveUrlFeed(UrlFeed urlFeed) throws ClassNotFoundException, SQLException {
        int pk = urlFeed.link.hashCode();
        loadDriver();
        PreparedStatement psInsert = null;
        ResultSet rs = null;
        String dbName = "UrlDB";
        try (Connection conn = DriverManager.getConnection(protocol + dbName + ";create=true",
                               props);
             PreparedStatement s = conn.prepareStatement("SELECT COUNT(id) FROM UrlFeed WHERE id = ?")) {
            s.setInt(1, pk);
            rs = s.executeQuery();
            rs.next();
            int count = rs.getInt(1);
            if (count == 0) {
                psInsert = conn.prepareStatement("INSERT INTO UrlFeed VALUES (?, ?, ?)");
                psInsert.setInt(1, pk);
                String escapeTitle = urlFeed.channelTitle.replaceAll("\'", "''");
                psInsert.setString(2, escapeTitle);
                psInsert.setString(3, urlFeed.link);
                count = psInsert.executeUpdate();
                System.out.println("Inserted " + urlFeed.channelTitle + " " + urlFeed.link);
            }
        }
        finally {
            close(rs);
            close(psInsert);
        }
        return pk;
    }

    private static void close(AutoCloseable closable) {
        try {
            if (closable != null) {
                closable.close();
                closable = null;
            }
        }
        catch (Exception sqle) {
            sqle.printStackTrace();
        }
    }

    private static void loadDriver() throws ClassNotFoundException {
        if (!loaded) {
            Class.forName(driver);
            System.out.println("Loaded driver");
            loaded = true;
        }
    }
}

班级 UrlFeed ```
import java.util.ArrayList;
import java.util.List;

public class UrlFeed {
int id;
String channelTitle = "News...";
String link;
List news = new ArrayList<>();

public String toString() {
    return String.format("urlFeed{id=%s, channelTitle=%s, link=%s, news=%s}",
                         id,
                         channelTitle,
                         link,
                         news);
}

public UrlFeed() {
}

public UrlFeed(String title, String link) {
    this.channelTitle = title;
    this.link = link;
}

}

班级 `NewsArticle` ```
public class NewsArticle {
    String title;
    String description;
    String link;
    String pubDate;

    public String toString() {
        return String.format("NewsArticle{title=%s, description=%s, link=%s, pubDate=%s, enclosure=}",
                             title,
                             description,
                             link,
                             pubDate);
    }
}

目前上述代码只打印到标准输出。您应该更改它，以便通过gui让用户知道程序正在做什么。例如，在加载网页时，可以显示进度指示器。什么时候 WebEngine 无法加载输入的url，您可能会显示警报。

编辑

在回复您的评论时，您写道：
webview似乎没有在右下角加载。有什么建议吗？
我相信你指的是局部变量 websiteView in方法 start 班级 DisplayContentsFromDatabase ，即。

final WebView websiteView = new WebView();

代码中唯一引用该变量的部分如下（也在方法中 start ):

newsBrief.getEngine().setOnAlert(new EventHandler<WebEvent<String>>() {
    public void handle(WebEvent<String> evt) {
        websiteView.getEngine().load(evt.getData());
    }
});

这里引用了javadoc的方法 setOnAlert :
设置属性onalert的值。
de属性scription:javascript alert 处理程序属性。当网页上运行的脚本调用alert函数时，将调用此处理程序。
因此，您需要为包含javascript的网页输入一个url，javascript将显示一个警报。只有这样，代码才会尝试加载某些内容并在中显示它 websiteView . 请原谅，我不打算测试代码。

java—尝试创建javafx应用程序，允许用户轻松地监视和维护嵌入式derby数据库中的网站列表

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