Vaadin 8.5.1- Refresh grid after row update

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青春惊慌失措
青春惊慌失措 2020-12-22 01:26

I am using Vaadin 8.5.1 Grid to display 1000\'s of rows. Once a row is updated with change in it property, I use grid.getDataProvider().refreshItem(selectedRow)

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  • 2020-12-22 02:09

    For a item to be seen as the same item, (and the refresh working) you need a corretly implemented equals() and hashCode() methods on the object.

    From the documentation

    public void refreshItem(T​ item)

    Description copied from interface: DataProvider

    Refreshes the given item. This method should be used to inform all DataProviderListeners that an item has been updated or replaced with a new instance.

    For this to work properly, the item must either implement

    equals(​Object) and #hashCode() to consider both the old and the new item instances to be equal, or alternatively

    DataProvider.​getId(​Object) should be implemented to return an appropriate identifier.

    In addition to this, it's you should create a ListDataProvider, assign it to the grid and then do the updated via the same instance of the previously assigned ListDataProvider

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  • 2020-12-22 02:09

    As the correct Answer by Schild said, you must override your equals and hashCode methods in such away that they consider the same field(s), and they must only consider field(s) whose values will not be changing during the time frame when you depend on them.

    For data-driven business objects, this usually means simply looking at the identifier on the object that is your primary key in a database (or would be if you used a database).

    As seen in the example below, our Status class has a UUID object as its identifier, a universally unique identifier (UUID) (a 128-bit value, canonically displayed as a 36-character hex string with hyphens). Our equals and hashCode considers only that one member of the object.

    @Override
    public boolean equals ( Object obj ) {  // Compare the UUID member named `uuid`.
        if ( obj == this ) { return true; }
        if ( obj instanceof Status ) { return this.getUuid().equals( ( ( Status ) obj ).getUuid() ); }
        return false;
    }
    
    @Override
    public int hashCode () {
        return Objects.hashCode( this.uuid );
    }  // Compare the UUID member named `uuid`.
    

    Example app

    Here is a complete working example. Written for Vaadin 8.5.

    In this example, we track three pieces of equipment. A Status object represents each.

    We modify the current status number (-1, 0, or 1) by choosing a new value number from the pop-up menu (a NativeSelect in Vaadin), and clicking a button for which piece of equipment. Selecting a row is irrelevant here.

    For your edification, I wrote two different pieces of code for updating the item in the Grid. Both approaches are common in Vaadin business apps:

    • Modifying the existing Status object backing the Grid.
    • Replace the target Status object with a fresh instance, but using the same identifier value in its id field.

    For example, in some cases, a data repository service code may be written to always return a fresh instance. In other cases, we may intentionally be updating an existing object with changes.

        private void updateByModifying ( Status s , Integer integer ) {
            s.setCurrentStatus( integer );
            grid.getDataProvider().refreshItem( s );
        }
    
        private void updateByInstantiating ( Status s , Integer integer ) {
            boolean removed = statuses.remove( s );
            Status replacement = new Status( s.getUuid() , s.getName() , integer );
            boolean added = statuses.add( replacement );
            grid.getDataProvider().refreshItem( replacement );
        }
    

    In this demo, switch between these approaches with the Update row by pop-up menu (also known as a drop-down list). Both of these approaches work by calling DataProvider::refreshItem. Note that both of these approaches depend on your equals and hashCode being properly implemented.

    As a further example, I threw in a Refresh all button to show the use of DataProvider::refreshAll method.

    Source code

    Three Java files in this example app:

    • MyUI.java (entry into Vaadin)
    • Status.java (our business object, POJO)
    • StatusLayout (the UI content and business logic)

    MyUI.java

    package com.basilbourque.example;
    
    import javax.servlet.annotation.WebServlet;
    
    import com.vaadin.annotations.Theme;
    import com.vaadin.annotations.VaadinServletConfiguration;
    import com.vaadin.server.VaadinRequest;
    import com.vaadin.server.VaadinServlet;
    import com.vaadin.ui.*;
    
    import java.util.List;
    import java.util.UUID;
    
    /**
     * This UI is the application entry point. A UI may either represent a browser window
     * (or tab) or some part of an 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 {
    
        @Override
        protected void init ( VaadinRequest vaadinRequest ) {
            Layout layout = new StatusLayout();
            this.setContent( layout );
        }
    
        @WebServlet ( urlPatterns = "/*", name = "MyUIServlet", asyncSupported = true )
        @VaadinServletConfiguration ( ui = MyUI.class, productionMode = false )
        public static class MyUIServlet extends VaadinServlet {
        }
    }
    

    Status.java

    package com.basilbourque.example;
    
    import java.util.Objects;
    import java.util.UUID;
    
    public class Status {
        // Members.
        private UUID uuid;
        private String name;
        private Integer currentStatus;  // 1 = Good, 0 = okay, -1 = Bad.
    
        // Constructor.
        public Status ( UUID uuid , String name , Integer currentStatus ) {
            this.uuid = uuid;
            this.name = name;
            this.currentStatus = currentStatus;
        }
    
        // -----------|  Object  |-------------------------
    
        @Override
        public boolean equals ( Object obj ) {  // Compare the UUID member named `uuid`.
            if ( obj == this ) { return true; }
            if ( obj instanceof Status ) { return this.getUuid().equals( ( ( Status ) obj ).getUuid() ); }
            return false;
        }
    
        @Override
        public int hashCode () {
            return Objects.hashCode( this.uuid );
        }  // Compare the UUID member named `uuid`.
    
        @Override
        public String toString () {
            return "Status{ " +
            "uuid=" + uuid +
            " | name='" + name + '\'' +
            " | currentStatus=" + currentStatus +
            " }";
        }
    
        // -----------|  Accessors  |-----------------------------
    
        public UUID getUuid () {
            return uuid;
        }
    
        public void setUuid ( UUID uuid ) {
            this.uuid = uuid;
        }
    
        public String getName () {
            return name;
        }
    
        public void setName ( String name ) { this.name = name; }
    
        public Integer getCurrentStatus () {
            return currentStatus;
        }
    
        public void setCurrentStatus ( Integer currentStatus ) {
            this.currentStatus = currentStatus;
        }
    }
    

    StatusLayout.java

    package com.basilbourque.example;
    
    import com.vaadin.data.provider.ListDataProvider;
    import com.vaadin.ui.*;
    
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Optional;
    import java.util.UUID;
    
    public class StatusLayout extends VerticalLayout {
        // Members
        List< Status > statuses;
        Grid< Status > grid;
    
        final List< Integer > numbers = List.of( 1 , 0 , - 1 );
        NativeSelect< Integer > numberPopup;
        NativeSelect< Boolean > updatyByModifyingOrInstantiating;
        Button setPump, setCamera, setSensor, refreshAllButton;
    
        // Constructor
        public StatusLayout () {
    
            statuses = new ArrayList<>( 3 );
            statuses.add( new Status( UUID.fromString( "1c0d183e-c2ba-11e8-a355-529269fb1459" ) , "Pump" , numbers.get( 0 ) ) );
            statuses.add( new Status( UUID.fromString( "2490c74e-1aac-4d71-9a2c-880628dcfc28" ) , "Camera" , numbers.get( 1 ) ) );
            statuses.add( new Status( UUID.fromString( "6ae07414-f557-4a1e-a552-cb5ec5f48476" ) , "Sensor" , numbers.get( 2 ) ) );
    
            // Create a grid bound to the list
            grid = new Grid<>( Status.class );
            grid.setCaption( "Equipment Status" );
            grid.setItems( statuses );
    //        grid.addColumn( Status :: getName ).setCaption( "Name" );
    //        grid.addColumn( Status :: getCurrentStatus ).setCaption( "Status" );
    
            updatyByModifyingOrInstantiating = new NativeSelect<>( "Update row by: " , List.of( Boolean.TRUE , Boolean.FALSE ) );
            updatyByModifyingOrInstantiating.setValue( Boolean.TRUE );
            updatyByModifyingOrInstantiating.setItemCaptionGenerator( ( ItemCaptionGenerator< Boolean > ) item -> item ? "modifying" : "instantiating" );
    
            Label valueSetterLabel = new Label( "Set status:" );
            numberPopup = new NativeSelect<>();
            numberPopup.setItems( numbers );
            numberPopup.setValue( numbers.get( 1 ) );
    //        numberPopup.setItemCaptionGenerator( item -> List.of( "Good" , "Okay" , "Bad" ).get( numbers.indexOf( item ) ) );  // Display words rather than the underlying number.
    
            // The `buttonClick` method below has logic depending on match between button name and `name` property on `Status` objects in grid.
            setPump = new Button( statuses.get( 0 ).getName() );  // Pump
            setPump.addClickListener( this :: buttonClick );
            setCamera = new Button( statuses.get( 1 ).getName() ); // Camera
            setCamera.addClickListener( this :: buttonClick );
            setSensor = new Button( statuses.get( 2 ).getName() );   // Sensor
            setSensor.addClickListener( this :: buttonClick );
    
            refreshAllButton = new Button( "Refresh all" );
            refreshAllButton.addClickListener( clickEvent -> grid.getDataProvider().refreshAll() );
    
            // Arrange
            grid.setWidth( 100 , Unit.PERCENTAGE );
    
            HorizontalLayout valueSetterBar = new HorizontalLayout();
            valueSetterBar.addComponents( valueSetterLabel , numberPopup , setPump , setCamera , setSensor );
            valueSetterBar.setComponentAlignment( valueSetterLabel , Alignment.MIDDLE_CENTER );
            valueSetterBar.setComponentAlignment( numberPopup , Alignment.MIDDLE_CENTER );
            valueSetterBar.setComponentAlignment( setPump , Alignment.MIDDLE_CENTER );
            valueSetterBar.setComponentAlignment( setCamera , Alignment.MIDDLE_CENTER );
            valueSetterBar.setComponentAlignment( setSensor , Alignment.MIDDLE_CENTER );
    
            addComponents( grid , updatyByModifyingOrInstantiating , valueSetterBar , refreshAllButton );
        }
    
        private void buttonClick ( Button.ClickEvent clickEvent ) {
            System.out.println( "TRACE - Setting " + clickEvent.getButton().getCaption() + " to " + this.numberPopup.getValue().toString() );
            // Find the `Status` object in the `List` whose name matches the name of the button clicked by user.
            Optional< Status > optionalStatus = statuses.stream().filter( status -> status.getName().equals( clickEvent.getButton().getCaption() ) ).findFirst();
            // We expect the matching `Status` to always be found. If not, throw exception.
            Status s = optionalStatus.orElseThrow( () -> new IllegalStateException( "Failed to find expected item in list of statuses: " + clickEvent.getButton().getCaption() ) );
            Integer valueToSet = this.numberPopup.getValue();
            // Set the `currentStatus` property on the `Status` object to the value of the selected popup menu item.
            // Try either updating by modifying existing row or by instantiating a new one.
            // Comment-out either of the next two lines.
            if(updatyByModifyingOrInstantiating.getValue().equals( Boolean.TRUE )) {
                this.updateByModifying( s , valueToSet );
            } else {
                this.updateByInstantiating( s , valueToSet );
            }
        }
    
        private void updateByModifying ( Status s , Integer integer ) {
            s.setCurrentStatus( integer );
            grid.getDataProvider().refreshItem( s );
        }
    
        private void updateByInstantiating ( Status s , Integer integer ) {
            boolean removed = statuses.remove( s );
            Status replacement = new Status( s.getUuid() , s.getName() , integer );
            boolean added = statuses.add( replacement );
            grid.getDataProvider().refreshItem( replacement );
        }
    }
    
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