Vaadin web应用程序连接到MySQL数据库不工作

Question

我正面临一个关于我在Vaadin上制作的web应用程序的问题。我下载了一个现成的Vaadin网络应用程序，连接到MySQL数据库，检查它是如何工作的。一切似乎都很顺利。有一个基本的选项卡，其中包含数据库数据的网格和一个表单，用于在数据库中添加或删除更多项。

我做了一些改变，比如在web应用程序中增加一些标签，或者改变主题和外观，没有遇到任何问题。

然后，我尝试通过Workbench在我的数据库中添加一些新列，这就是问题开始的时候。每次我尝试添加一个新的列在数据库中，网格在web应用程序消失，但我没有得到任何错误....

更具体地说:

-I首先通过工作台添加名为"examination_type">

的新列来修改表。ALTER TABLE dummydata.employees ADD COLUMN examination_type VARCHAR(1000);

-其次，我在Java类中添加了examination_type字段(现在它出现在构造函数、getter和setter中)

private String firstname;
private String lastname;
private String examination_type;
private String email;
private String notes;

public Employee(String firstname, String lastname, String examination_type, String email, String notes) {
super();
this.firstname = firstname;
this.lastname = lastname;
this.examination_type = examination_type;
this.email = email;
this.notes = notes;
}
//Getters and Setters

-然后我在需要的后端服务文件中添加了字段:

@Component
public class EmployeeService {

@Autowired
private JdbcTemplate jdbcTemplate;
public List<Employee> findAll() {       
try {
return jdbcTemplate.query("SELECT firstname, lastname, email, examination_type FROM employees",
(rs, rowNum) -> new Employee(rs.getString("firstname"), rs.getString("lastname"), rs.getString("examination_type"), rs.getString("email"), rs.getString("notes")));
} catch (Exception e) {
return new ArrayList<Employee>();   
}       
}

public List<Employee> findByEmail(String email) {       
try {
return jdbcTemplate.query("SELECT firstname, lastname, email, examination_type FROM employees WHERE email = ?",
new Object[]{email},
(rs, rowNum) -> new Employee(rs.getString("firstname"), rs.getString("lastname"), rs.getString("examination_type"), rs.getString("email"), rs.getString("notes")));
} catch (Exception e) {
return new ArrayList<Employee>();   
}       
}

public int saveEmployee(Employee employee) {
List<Employee> employees = this.findByEmail(employee.getEmail());
if ( employees.size() > 0 ) {
return updateEmployee(employee);
} else {
return insertEmployee(employee);
}

}

private int updateEmployee(Employee employee) {     
try {
return jdbcTemplate.update("UPDATE employees SET lastname = ?, firstname = ?, examination_type = ? WHERE email = ?",
employee.getLastname(), employee.getFirstname(), employee.getExaminationType(), employee.getEmail());
} catch (Exception e) {
return 0;
}
}

private int insertEmployee(Employee employee) {
try {
return jdbcTemplate.update("INSERT INTO employees VALUES (?, ?, ?, ?, ?)",
employee.getFirstname(), employee.getLastname(), employee.getExaminationType(), employee.getEmail(),  "" /*employee.getBirthDate()*/);
} catch (Exception e) {
return 0;
}       
}

public int deleteEmployee(Employee employee) {
try {
return jdbcTemplate.update("DELETE FROM employees WHERE email = ?",
employee.getEmail());
} catch (Exception e) {
return 0;
}
}
}

-最后但并非最不重要的，我在我的表单中添加了考试类型Textfield

当我编译程序时没有错误，我甚至得到了一个"前端编译成功"。消息。然后我访问localhost网站和网格，在那里我应该看到我的数据库内容，没有出现。但是，表单工作得很好，我可以在数据库中添加新项。

任何想法?

很抱歉写了这么久!

下面是视图的代码:

@Route(value = "examinations", layout = MainView.class)
@PageTitle("Examinations")
@CssImport("styles/views/examinations/examinations-view.css")
public class ExaminationsView extends Div implements AfterNavigationObserver {
@Autowired
private EmployeeService employeeService;
private Grid<Employee> employees;
private TextField firstname = new TextField();
private TextField lastname = new TextField();
private TextField email = new TextField();
private TextField examination_type = new TextField();
private Button cancel = new Button("Cancel");
private Button save = new Button("Save");
private Button delete = new Button("Delete");

private Binder<Employee> binder;
public ExaminationsView() {
setId("examinations-view");
// Configure Grid
employees = new Grid<>();
employees.addThemeVariants(GridVariant.LUMO_NO_BORDER);
employees.setHeightFull();
employees.addColumn(Employee::getFirstname).setHeader("First name");
employees.addColumn(Employee::getLastname).setHeader("Last name");
employees.addColumn(Employee::getEmail).setHeader("Email");
employees.addColumn(Employee::getExaminationType).setHeader("Examination Type");
//when a row is selected or deselected, populate form
employees.asSingleSelect().addValueChangeListener(event -> populateForm(event.getValue()));
// Configure Form
binder = new Binder<>(Employee.class);
binder.bindInstanceFields(this);
binder.setBean(new Employee());

cancel.addClickListener(e -> employees.asSingleSelect().clear());
save.addClickListener(e -> {
Employee employee = binder.getBean();
if ( employeeService.saveEmployee(employee) > 0) {
employees.setItems(employeeService.findAll());
} else {
Notification.show("Save error");
}               
});

delete.addClickListener(e -> {
Employee employee = binder.getBean();
if ( employeeService.deleteEmployee(employee) > 0) {
employees.setItems(employeeService.findAll());
} else {
Notification.show("Delete error");
}               
});
SplitLayout splitLayout = new SplitLayout();
splitLayout.setSizeFull();
createGridLayout(splitLayout);
createEditorLayout(splitLayout);
add(splitLayout);
}

private void createEditorLayout(SplitLayout splitLayout) {
Div editorDiv = new Div();
editorDiv.setId("editor-layout");
FormLayout formLayout = new FormLayout();
addFormItem(editorDiv, formLayout, firstname, "First name");
addFormItem(editorDiv, formLayout, lastname, "Last name");
addFormItem(editorDiv, formLayout, email, "Email");
addFormItem(editorDiv, formLayout, examination_type, "Examination Type");
createButtonLayout(editorDiv);
splitLayout.addToSecondary(editorDiv);
}
private void createButtonLayout(Div editorDiv) {
HorizontalLayout buttonLayout = new HorizontalLayout();
buttonLayout.setId("button-layout");
buttonLayout.setWidthFull();
buttonLayout.setSpacing(true);
cancel.addThemeVariants(ButtonVariant.LUMO_TERTIARY);
save.addThemeVariants(ButtonVariant.LUMO_PRIMARY);
delete.addThemeVariants(ButtonVariant.LUMO_ERROR);
buttonLayout.add(delete, cancel, save);
editorDiv.add(buttonLayout);
}
private void createGridLayout(SplitLayout splitLayout) {
Div wrapper = new Div();
wrapper.setId("wrapper");
wrapper.setWidthFull();
splitLayout.addToPrimary(wrapper);
wrapper.add(employees);
}
private void addFormItem(Div wrapper, FormLayout formLayout, AbstractField field, String fieldName) {       
formLayout.addFormItem(field, fieldName);
wrapper.add(formLayout);
field.getElement().getClassList().add("full-width");
}

@Override
public void afterNavigation(AfterNavigationEvent event) {
employees.setItems(employeeService.findAll());
}
private void populateForm(Employee value) {
if ( value == null ) {
value = new Employee();
}
binder.setBean(value);

}
}

Answer 1

距离我发布这篇文章已经几个小时了，距离问题第一次发生已经有几天了。最后，似乎我是通过MySQL参数在一个不同的序列比一个在数据库内?把它们纠正过来似乎就成功了。谢谢大家，记住并检查参数....