JAVA - 使用套接字和线程接收对象不工作
问题描述：
我试图从服务器获取一个对象，但它不工作。
I'm trying to get an object from the server, but it does not work.
服务器的相关部分（通过Debug我看到他真的发送正确的对象）：
Relevant section from the server (By Debug I see that he is really sending the correct object):
public static void main(String[] args){
launch(args);
}
public void start(Stage primaryStage) {
BorderPane mainPane = new BorderPane();
mainPane.setStyle("-fx-border-color: black;");
mainPane.setPadding(new Insets(5,5,5,5));
GridPane gridPane = new GridPane();
gridPane.setPadding(new Insets(5,5,5,5));
gridPane.add(lblStatus,0,1);
gridPane.add(lblDate,0,2);
mainPane.setTop(gridPane);
createTableView();
mainPane.setCenter(tableView);
Scene scene = new Scene(mainPane, 700, 250);
primaryStage.setTitle("Server"); // Set the window title
primaryStage.setScene(scene); // Place the scene in the window
primaryStage.show(); // Display the window
primaryStage.setAlwaysOnTop(true);
primaryStage.setOnCloseRequest(
new EventHandler<WindowEvent>(){
public void handle(WindowEvent event) {
try {
Platform.exit();
System.exit(0);
serverSocket.close();
socket.close();
}
catch(SocketException ex){
try {
socket.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
catch (IOException e) {
// TODO Auto-generated catch block
Platform.exit();
System.exit(0);
}
}
});
connectToDB();
connectionDate=new Date();
Platform.runLater(() ->lblDate.setText(("Server started at \t"+connectionDate)));
Platform.runLater(() ->lblStatus.setText(connectionStatus));
new Thread( () ->
{
try{
// Create a server socket
serverSocket = new ServerSocket(8000);
while (true){
// Listen for a connection request
socket = serverSocket.accept();
this.clientNo++;
clientRequest clientDetails = new clientRequest(clientNo, new Date(), "New Clinet");
addRowToServerTable(clientDetails);
new Thread(new HandleAClient(socket)).start();
}
}
catch(SocketException ex){
}
catch(IOException ex){
}
}).start();
}
/** Connect to DB */
private void connectToDB(){
// Connection to the database
try{
Class.forName(driver); // Load the JDBC driver
System.out.println("Driver Loaded");
connection = DriverManager.getConnection(url, username, password); // Establish a connection
System.out.println("Connected to " + url);
connectionStatus = "Connected to \t" + url;
}
catch (java.lang.Exception ex){
ex.printStackTrace();
connectionStatus = ex.toString();
}
}
// Define the thread class for handling new connection
class HandleAClient implements Runnable{
private Socket socket; // A connected socket
/** Construct a thread */
public HandleAClient(Socket socket){
this.socket = socket;
}
/** Run a thread */
public void run(){
try{
// Create data input and output streams
ObjectOutputStream outputToClient = new ObjectOutputStream(
socket.getOutputStream());
DataInputStream inputFromClient = new DataInputStream(
socket.getInputStream());
// Continuously serve the client
while (true){
// Receive sql from the client
String sql = inputFromClient.readUTF();
clientRequest clientDetails = new clientRequest(clientNo, new Date(),"New Query");
addRowToServerTable(clientDetails);
// Execute SQL
Object[] rows = executeSQL(sql);
outputToClient.writeObject(rows);
}
}
catch(SocketException ex){
try{
serverSocket.close();
//socket.close();
}
catch (IOException e){
}
}
catch(IOException ex){
}
}
客户端的相关部分（可能是客户端上的错误，当它接收到跳转线的对象.start ;Of the Thread。）：
Relevant section from the client (Probably the mistake on the client, when it receives the object he jumps line ".start ();" Of the Thread.):
private void connectToServer(){
try{
// Create a socket to connect to the server
socket = new Socket(host, 8000);
// Create an input stream to receive Object from the server
fromServer = new ObjectInputStream(socket.getInputStream());
// Create an output stream to send data to the server
toServer = new DataOutputStream(socket.getOutputStream());
}
catch (Exception ex){
ex.printStackTrace();
}
}
private void sendAndGetFromServer(String sqlQuery){
new Thread(() ->{
try{
System.out.println("a1");
// Send sql query to server
toServer.writeUTF(sqlQuery);
//toServer.flush();
// Get notification from the server
Student[] rows = (Student[])fromServer.readObject();
setRowsInTable(rows);
}
catch(SocketException ex){
try{
socket.close();
}
catch (IOException e){
}
}
catch (Exception ex){
}
}).start();
我试图分成两个线程（一个输入和其他输出在服务器和客户端）根据答案我读这里---但它没有帮助。
也尝试更改输入和输出顺序---未成功。
I tried to separate into two Thread (One Input and other Output in Server and client) according to the answers I read here --- but it didn't help. Also tried to change the order of Input and Output --- without success.
- 没有错误！
- 客户没有获得对象。
这里有什么问题？
编辑。学生类：
public class Student implements Externalizable
{
private final SimpleIntegerProperty ID;
private final SimpleStringProperty firstName;
private final SimpleStringProperty lastName;
private final SimpleStringProperty address;
private final SimpleObjectProperty<Date> birthDate;
private final SimpleStringProperty department;
private final SimpleIntegerProperty pointsAmount;
private final SimpleObjectProperty<Date> startStudyingDate;
private final SimpleIntegerProperty failedAmount;
private final SimpleDoubleProperty average;
private final SimpleIntegerProperty lavelByGrade;
private final SimpleStringProperty pic;
public Student(int ID, String firstName, String lastName, String address,
Date birthDate, String department,
int pointsAmount, Date startStudyingDate, int failedAmount,
double average, int lavelByGrade, String pic){
this.ID= new SimpleIntegerProperty(ID);
this.firstName= new SimpleStringProperty(firstName);
this.lastName= new SimpleStringProperty(lastName);
this.address= new SimpleStringProperty(address);
this.birthDate= new SimpleObjectProperty<Date>(birthDate);
this.department= new SimpleStringProperty(department);
this.pointsAmount= new SimpleIntegerProperty(pointsAmount);
this.startStudyingDate= new SimpleObjectProperty<Date>(startStudyingDate);
this.failedAmount= new SimpleIntegerProperty(failedAmount);
this.average= new SimpleDoubleProperty(average);
this.lavelByGrade= new SimpleIntegerProperty(lavelByGrade);
this.pic = new SimpleStringProperty(pic);
}
public int getID() {
return ID.get();
}
public void setID(int ID) {
this.ID.set(ID);
}
public String getFirstName() {
return firstName.get();
}
public void setFirstName(String firstName) {
this.firstName.set(firstName);
}
public String getLastName() {
return lastName.get();
}
public void setLastName(String lastName) {
this.lastName.set(lastName);
}
public String getAddress() {
return address.get();
}
public void setAddress(String address) {
this.address.set(address);
}
public Date getBirthDate() {
return birthDate.get();
}
public void setBirthDate(Date birthDate) {
this.birthDate.set(birthDate);
}
public String getDepartment() {
return department.get();
}
public void setDepartment(String department) {
this.department.set(department);
}
public int getPointsAmount() {
return pointsAmount.get();
}
public void setPointsAmount(int pointsAmount) {
this.pointsAmount.set(pointsAmount);
}
public Date getStartStudyingDate() {
return startStudyingDate.get();
}
public void setStartStudyingDate(Date startStudyingDate) {
this.startStudyingDate.set(startStudyingDate);
}
public int getFailedAmount() {
return failedAmount.get();
}
public void setFailedAmount(int failedAmount) {
this.failedAmount.set(failedAmount);
}
public double getAverage() {
return average.get();
}
public void setAverage(Double average) {
this.average.set(average);
}
public int getLavelByGrade() {
return lavelByGrade.get();
}
public void setLavelByGrade(int lavelByGrade) {
this.lavelByGrade.set(lavelByGrade);
}
public String getPic() {
return pic.get();
}
public void setPic(String pic) {
this.pic.set(pic);
}
@Override
public void readExternal(ObjectInput in) throws IOException,
ClassNotFoundException {
setID(in.readInt());
setFirstName((String)in.readObject());
setLastName((String)in.readObject());
setAddress((String)in.readObject());
setBirthDate((Date)in.readObject());
setDepartment((String)in.readObject());
setPointsAmount(in.readInt());
setStartStudyingDate((Date)in.readObject());
setFailedAmount(in.readInt());
setAverage(in.readDouble());
setLavelByGrade(in.readInt());
setPic((String)in.readObject());
}
@Override
public void writeExternal(ObjectOutput out) throws IOException {
out.writeInt(getID());
out.writeObject(getFirstName());
out.writeObject(getLastName());
out.writeObject(getAddress());
out.writeObject(getBirthDate());
out.writeObject(getDepartment());
out.writeInt(getPointsAmount());
out.writeObject(getStartStudyingDate());
out.writeInt(getFailedAmount());
out.writeDouble(getAverage());
out.writeInt(getLavelByGrade());
out.writeObject(getPic());
}
}
答
JavaFX属性不可序列化。因此，如果你尝试序列化一个使用JavaFX属性的对象的状态，你会得到一个异常。
JavaFX properties are not Serializable. So if you try to serialize an object that uses JavaFX properties for its state, you will get an exception.
这里有几个选项。一个是简单地不使用Java对象序列化，而是一些其他的序列化技术，例如用JSON表示对象。
You have a couple of options here. One is simply to not use Java object serialization, but some other serialization technique, such as representing the object with JSON.
另一个选项是实现 Externalizable 而不是 Serializable 。 可外化是 Serializable 的子接口，您可以在其中定义自己的用于序列化和反序列化数据的过程。特别是，不是序列化JavaFX属性本身，而是序列化它们的内容。
The other option is to implement Externalizable instead of Serializable. Externalizable is a subinterface of Serializable in which you define your own process for serializing and deserializing the data. In particular, instead of serializing the JavaFX properties themselves, just serialize their contents.
一个简单的例子：
import java.io.Externalizable ;
import java.io.IOException ;
import java.io.ObjectInput ;
import java.io.ObjectOutput ;
import javafx.beans.property.IntegerProperty ;
import javafx.beans.property.SimpleIntegerProperty ;
import javafx.beans.property.SimpleStringProperty ;
import javafx.beans.property.StringProperty ;
public class Person implements Externalizable {
private final StringProperty name = new SimpleStringProperty();
private final IntegerProperty id = new SimpleIntegerProperty();
public StringProperty nameProperty() {
return name ;
}
public final String getName() {
return nameProperty().get();
}
public final void setName(String name) {
nameProperty().set(name);
}
public IntegerProperty idProperty() {
return id ;
}
public final int getId() {
return idProperty().get();
}
public final void setId(int id) {
idProperty().set(id);
}
// important: must have a no-arg constructor:
public Person() { }
public Person(int id, String name) {
setId(id);
setName(name);
}
@Override
public void writeExternal(ObjectOutput out) throws IOException {
// write id then name
// note we write the contents of the properties, not the properties
// themselves, as the properties are not serializable:
out.writeInt(getId());
out.writeObject(getName());
}
@Override
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
// read data back in same order:
setId(in.readInt());
setName((String)in.readObject());
}
}
注意，这个类有一个非常简单的结构，它很容易实现这两种方法。
Note that this class has a pretty simple structure, so it's easy to implement these two methods. For more complex objects - particularly those which may potentially have circular references - you need to work a bit harder.
由于上面定义的类实现了 Externalizable（），因此对于更复杂的对象（特别是那些可能有循环引用的对象） ，它还实现了 Serializable ，并且可以以通常的方式序列化：
Since the class defined above implements Externalizable, it also implements Serializable, and can be serialized in the usual way:
ObjectOutputStream oos = ... ;
oos.writeObject(new Person(007, "James Bond"));
阅读我的博客文章 JavaFX bean和JPA 。