java - Vaadin 8 `Binder::bindInstanceFields` 是否仅适用于 String 数据类型？

Question

使用 Vaadin 8 @PropertyId带有 Binder::bindInstanceFields 的注释肯定比为每个字段属性绑定(bind)编写一行代码更短、更甜美。

Person person;  // `name` is String, `yearOfBirth` is Integer.
…
@PropertyId ( "name" )
final TextField nameField = new TextField ( "Full name:" ); // Bean property.

@PropertyId ( "yearOfBirth" )
final TextField yearOfBirthField = new TextField ( "Year of Birth:" ); // Bean property.
…
// Binding
Binder < Person > binder = new Binder <> ( Person.class );
binder.bindInstanceFields ( this );
binder.setBean ( person );

但我们会抛出异常，因为 yearOfBirth 属性是一个整数，而且这种简单易行的绑定(bind)方法缺少转换器。

SEVERE:

java.lang.IllegalStateException: Property type 'java.lang.Integer' doesn't match the field type 'java.lang.String'. Binding should be configured manually using converter.

这是否意味着 Binder::bindInstanceFields只能使用完全由 String 数据类型的属性组成的 bean 吗？

有没有办法指定一个 Converter例如StringToIntegerConverter无需逐条列出代码中的每个绑定(bind)？

Answer 1

参见 Vaadin Framework, Vaadin Data Model, Binding Data to Forms :

Conversions

You can also bind application data to a UI field component even though the types do not match.

Binder#bindInstanceFields() 说:

It's not always possible to bind a field to a property because their types are incompatible. E.g. custom converter is required to bind HasValue<String> and Integer property (that would be a case of "age" property). In such case IllegalStateException will be thrown unless the field has been configured manually before calling the bindInstanceFields(Object) method.

[...]: the bindInstanceFields(Object) method doesn't override existing bindings.

[我强调的。]

所以，AFAIU，这应该有效:

private final TextField siblingsCount = new TextField( "№ of Siblings" );

...

binder.forField( siblingsCount )
    .withNullRepresentation( "" )
    .withConverter(
        new StringToIntegerConverter( Integer.valueOf( 0 ), "integers only" ) )
    .bind( Child::getSiblingsCount, Child::setSiblingsCount );
binder.bindInstanceFields( this );

但它仍然抛出:

java.lang.IllegalStateException: Property type 'java.lang.Integer' doesn't match the field type 'java.lang.String'. Binding should be configured manually using converter.
...
at com.vaadin.data.Binder.bindInstanceFields(Binder.java:2135)
...

你在开玩笑吗？我就是这么做的，不是吗？我相当怀疑“没有覆盖现有绑定(bind)”。 或者，如果没有实际覆盖，它们似乎在 bindInstanceFields() 中被忽略了。 ，至少。

不使用 Binder#bindInstanceFields() 时，相同的手动绑定(bind)配置也有效但是每个字段都有单独绑定(bind)的方法。

另请参阅线程 Binding from Integer not working在 Vaadin 框架数据绑定(bind)论坛和 issue #8858 Binder.bindInstanceFields() overwrites existing bindings .

解决方法

比@cfrick 的回答更简单:

/** Used for workaround for Vaadin issue #8858
 *  'Binder.bindInstanceFields() overwrites existing bindings'
 *  https://github.com/vaadin/framework/issues/8858
 */
private final Map<String, Component> manualBoundComponents = new HashMap<>();
...
// Commented here and declared local below for workaround for Vaadin issue #8858 
//private final TextField siblingsCount = new TextField( "№ of Siblings" );
...

public ChildView() {
    ...

    // Workaround for Vaadin issue #8858
    // Declared local here to prevent processing by Binder#bindInstanceFields() 
    final TextField siblingsCount = new TextField( "№ of Siblings" );
    manualBoundComponents.put( "siblingsCount", siblingsCount );
    binder.forField( siblingsCount )
            .withNullRepresentation( "" )
            .withConverter( new StringToIntegerConverter( Integer.valueOf( 0 ), "integers only" ) )
            .bind( Child::getSiblingsCount, Child::setSiblingsCount );
    binder.bindInstanceFields( this );

    ...

    // Workaround for Vaadin issue #8858  
    addComponent( manualBoundComponents.get( "siblingsCount" ) );
    //addComponent( siblingsCount );

    ...
}

更新

Fix #8998 Make bindInstanceFields not bind fields already bound using functions .

source code for that fix至少出现在 Vaadin 8.1.0 alpha 4 pre-release 中(也许还有其他人)。

---

Basil Bourque 更新...

如上所示，您的想法是使用 Binder::bindInstanceFields在对不兼容(整数)属性进行手动绑定(bind)之后，确实对我有用。您提示在您的实验代码中调用了 Binder::bindInstanceFields未能遵循调用“不覆盖现有绑定(bind)”的记录行为。

但它似乎对我有用。这是 Vaadin 8.1.0 alpha 3 的示例应用程序。首先我手动绑定(bind) yearOfBirth属性(property)。然后我使用 binder.bindInstanceFields绑定(bind) @PropertyId注释 name属性(property)。这两个属性的字段显示已填充并响应用户编辑。

我是否遗漏了什么，或者它是否按照记录正常工作？如果我犯了错误，请删除此部分。

package com.example.vaadin.ex_formatinteger;

import com.vaadin.annotations.Theme;
import com.vaadin.annotations.VaadinServletConfiguration;
import com.vaadin.data.Binder;
import com.vaadin.data.converter.StringToIntegerConverter;
import com.vaadin.server.VaadinRequest;
import com.vaadin.server.VaadinServlet;
import com.vaadin.ui.*;

import javax.servlet.annotation.WebServlet;

/**
 * This UI is the application entry point. A UI may either represent a browser window
 * (or tab) or some part of a html page where a Vaadin application is embedded.
 * <p>
 * The UI is initialized using {@link #init(VaadinRequest)}. This method is intended to be
 * overridden to add component to the user interface and initialize non-component functionality.
 */
@Theme ( "mytheme" )
public class MyUI extends UI {
    Person person;

    //@PropertyId ( "honorific" )
    final TextField honorific = new TextField ( "Honorific:" ); // Bean property.

    //@PropertyId ( "name" )
    final TextField name = new TextField ( "Full name:" ); // Bean property.

    // Manually bind property to field.
    final TextField yearOfBirthField = new TextField ( "Year of Birth:" ); // Bean property.

    final Label spillTheBeanLabel = new Label ( ); // Debug. Not a property.

    @Override
    protected void init ( VaadinRequest vaadinRequest ) {
        this.person = new Person ( "Ms.", "Margaret Hamilton", Integer.valueOf ( 1936 ) );

        Button button = new Button ( "Spill" );
        button.addClickListener ( ( Button.ClickEvent e ) -> {
            spillTheBeanLabel.setValue ( person.toString ( ) );
        } );

        // Binding
        Binder < Person > binder = new Binder <> ( Person.class );
        binder.forField ( this.yearOfBirthField )
              .withNullRepresentation ( "" )
              .withConverter ( new StringToIntegerConverter ( Integer.valueOf ( 0 ), "integers only" ) )
              .bind ( Person:: getYearOfBirth, Person:: setYearOfBirth );
        binder.bindInstanceFields ( this );
        binder.setBean ( person );


        setContent ( new VerticalLayout ( honorific, name, yearOfBirthField, button, spillTheBeanLabel ) );
    }

    @WebServlet ( urlPatterns = "/*", name = "MyUIServlet", asyncSupported = true )
    @VaadinServletConfiguration ( ui = MyUI.class, productionMode = false )
    public static class MyUIServlet extends VaadinServlet {
    }
}

而且简单Person类。

package com.example.vaadin.ex_formatinteger;

import java.time.LocalDate;
import java.time.ZoneId;

/**
 * Created by Basil Bourque on 2017-03-31.
 */
public class Person {

    private String honorific ;
    private String name;
    private Integer yearOfBirth;

    // Constructor
    public Person ( String honorificArg , String nameArg , Integer yearOfBirthArg ) {
        this.honorific = honorificArg;
        this.name = nameArg;
        this.yearOfBirth = yearOfBirthArg;
    }

    public String getHonorific ( ) {
        return honorific;
    }

    public void setHonorific ( String honorific ) {
        this.honorific = honorific;
    }

    // name property
    public String getName ( ) {
        return name;
    }

    public void setName ( String nameArg ) {
        this.name = nameArg;
    }

    // yearOfBirth property
    public Integer getYearOfBirth ( ) {
        return yearOfBirth;
    }

    public void setYearOfBirth ( Integer yearOfBirth ) {
        this.yearOfBirth = yearOfBirth;
    }

    // age property. Calculated, so getter only, no setter.
    public Integer getAge ( ) {
        int age = ( LocalDate.now ( ZoneId.systemDefault ( ) )
                             .getYear ( ) - this.yearOfBirth );
        return age;
    }

    @Override
    public String toString ( ) {
        return "Person{ " +
                "honorific='" + this.getHonorific () + '\'' +
                ", name='" + this.getName ()  +
                ", yearOfBirth=" + this.yearOfBirth +
                ", age=" + this.getAge () +
                " }";
    }
}