Vaadin 8`Binder :: bindInstanceFields`只适用于String数据类型吗？

Question

使用Vaadin 8 @PropertyId注释Binder::bindInstanceFields肯定比为每个字段属性绑定编写一行代码更短更甜.

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 );

但是我们得到一个异常抛出,因为yearOfBirth属性是一个整数,这种简单的绑定方法缺少转换器.

严重:

java.lang.IllegalStateException:属性类型'java.lang.Integer'与字段类型'java.lang.String'不匹配.应使用转换器手动配置绑定.

这是否意味着Binder::bindInstanceFields只能使用完全由String数据类型属性构成的bean ？

有没有办法指定一个Converter这样的,StringToIntegerConverter而不必逐条列出代码中的每一个绑定？

Answer 1

请参阅Vaadin框架,Vaadin数据模型,将数据绑定到表单:

转换

您还可以将应用程序数据绑定到UI字段组件,即使类型不匹配也是如此.

Binder#bindInstanceFields() 说:

并不总是可以将字段绑定到属性,因为它们的类型不兼容.例如,自定义转换器需要绑定HasValue<String>和Integer属性(这将是"年龄"属性的情况).除非在调用方法之前手动配置了字段,否则IllegalStateException将抛出此类情况.bindInstanceFields(Object)

[...]:该bindInstanceFields(Object)方法不会覆盖现有绑定.

[由我强调.]

所以,AFAIU,这应该工作:

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) ...

你在跟我开玩笑吗？这就是我做的,不是吗？我更怀疑"不会覆盖现有的绑定".或者,如果实际上没有被覆盖,那么它们似乎bindInstanceFields()至少被忽略了.

相同的手动绑定配置在不使用时工作,Binder#bindInstanceFields()但对每个字段使用单独绑定的方法.

另请参阅线程Binding from Integer不在 Vaadin Framework数据绑定论坛中工作,问题#8858 Binder.bindInstanceFields()覆盖现有绑定.

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 );

    ...
}

UPDATE

修复#8998使bindInstanceFields不绑定已使用函数绑定的字段.

该修补程序的源代码至少出现在Vaadin 8.1.0 alpha 4预发行版(或许还有其他版本)中.

Basil Bourque更新......

您的想法,如上所示,Binder::bindInstanceFields在非兼容(整数)属性的手动绑定后使用确实似乎对我有用.您抱怨说,在您的实验代码中,调用Binder::bindInstanceFields未能遵循记录的行为,其中调用"不会覆盖现有绑定".

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yearOfBirth属性.然后我binder.bindInstanceFields用来绑定带@PropertyId注释的name属性.两个属性的字段将显示为已填充并响应用户编辑.

我是否遗漏了某些东西,或者这是否记录在案？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 {
    }
}

简单的Person课程.

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 () +
                " }";
    }
}