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

Question

使用 Vaadin 8 @PropertyId annotation with the Binder::bindInstanceFields 肯定比为每个字段编写一行代码-属性绑定更短、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 );

但是我们抛出了异常，因为 yearOfBirth 属性是一个整数，而这种简单易行的绑定方法缺少转换器。

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 只能用于完全由 String 数据类型的属性组成的 bean？

有没有一种方法可以指定 Converter such as StringToIntegerConverter 而不必逐项列出代码中的每个绑定？

Answer 1

到目前为止，对我来说处理这个问题的最好方法是为输入的类型（注意这个 "pattern" 也适用于编写复合字段）。

请在此处查看完整示例。 IntegerField 是包装 Integer 的字段在另一个活页夹中通过一个 bean 来保存实际值。

// run with `spring run --watch <file>.groovy`
@Grab('com.vaadin:vaadin-spring-boot-starter:2.0.1')

import com.vaadin.ui.*
import com.vaadin.annotations.*
import com.vaadin.shared.*
import com.vaadin.data.*
import com.vaadin.data.converter.*

class IntegerField extends CustomField<Integer> {
    final Binder<Bean> binder
    final wrappedField = new TextField()
    IntegerField() {
        binder = new BeanValidationBinder<IntegerField.Bean>(IntegerField.Bean)
        binder.forField(wrappedField)
            .withNullRepresentation('')
            .withConverter(new StringToIntegerConverter("Only numbers"))
            .bind('value')
        doSetValue(null)
    }
    IntegerField(String caption) {
        this()
        setCaption(caption)
    }
    Class<Integer> getType() {
        Integer
    }
    com.vaadin.ui.Component initContent() {
        wrappedField
    }
    Registration addValueChangeListener(HasValue.ValueChangeListener<Integer> listener) {
        binder.addValueChangeListener(listener)
    }
    protected void doSetValue(Integer value) {
        binder.bean = new IntegerField.Bean(value)
    }
    Integer getValue() {
       binder.bean?.value
    }
    @groovy.transform.Canonical
    static class Bean {
        Integer value
    }
}

@groovy.transform.Canonical
class Person {
    @javax.validation.constraints.Min(value=18l)
    Integer age
}

class PersonForm extends FormLayout {
    @PropertyId('age')
    IntegerField ageField = new IntegerField("Age")
    PersonForm() {
        addComponents(ageField)
    }
}

@com.vaadin.spring.annotation.SpringUI
@com.vaadin.annotations.Theme("valo")
class MyUI extends UI {
    protected void init(com.vaadin.server.VaadinRequest request) {
        def form = new PersonForm()
        def binder = new BeanValidationBinder<Person>(Person)
        binder.bindInstanceFields(form)
        binder.bean = new Person()
        content = new VerticalLayout(
            form, 
            new Button("Submit", {
                Notification.show(binder.bean.toString())
            } as Button.ClickListener)
        )
    }
}

Answer 2

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 "doesn't override existing bindings"。 或者，如果实际上没有被覆盖，它们似乎至少在 bindInstanceFields() 中被忽略了。

相同的手动绑定配置在不使用 Binder#bindInstanceFields() 时有效，但每个字段使用单独绑定的方法。

另请参阅线程 Binding from Integer not working in the Vaadin Framework Data Binding forum and 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 appears at least in Vaadin 8.1.0 alpha 4 pre-release（也许还有其他人）。

Basil Bourque 更新…

如上所示，在对不兼容（整数）属性进行手动绑定后使用 Binder::bindInstanceFields 的想法确实对我有用。您抱怨说，在您的实验代码中，对 Binder::bindInstanceFields 的调用未能遵循调用“不覆盖现有绑定”的记录行为。

但这似乎对我有用。这是 Vaadin 8.1.0 alpha 3 的示例应用程序。首先，我手动绑定 yearOfBirth 属性。然后我用binder.bindInstanceFields绑定@PropertyId注解name属性。这两个属性的字段显示已填充并响应用户编辑。

我是不是遗漏了什么，或者它是否按照记录正常工作？如果我有错误，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 {
    }
}

简单Personclass.

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 () +
                " }";
    }
}

Answer 3

问题在Vaadin 8.4.0 中依然存在，Converter 无法识别并不断抛出IllegalStateException。但是这个可怕的错误有一个简单的解决方法：

binder.bind(id, obj -> obj.getId() + "", null); //the ValueProvider "getter" could consider that getId returns null

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

Does Vaadin 8 `Binder::bindInstanceFields` only work with String data types?

java

data-binding

vaadin

vaadin8

Conversions

解决方法

更新