Question

我刚刚在展示代码中启用了“DataTable - Lazy Loading”

的多重排序

datatableLazy.xhtml

<html lang="en" xmlns="http://www.w3.org/1999/xhtml"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:p="http://primefaces.org/ui"
xmlns:ui="http://java.sun.com/jsf/facelets">
<h:head>
<title>CarDataTable</title>
</h:head>
<h:body>
<h:form id="form">
    <p:dataTable var="car" value="#{tableBean.lazyModel}" paginator="true"
        rows="10"
        paginatorTemplate="{RowsPerPageDropdown} {FirstPageLink} {PreviousPageLink} {CurrentPageReport} {NextPageLink} {LastPageLink}"
        rowsPerPageTemplate="5,10,15" id="carTable" lazy="true"
        sortMode="multiple">

        <p:ajax event="rowSelect" listener="#{tableBean.onRowSelect}"
            update=":form:display" oncomplete="carDialog.show()" />

        <p:column headerText="Model" sortBy="#{car.model}"
            filterBy="#{car.model}">
            <h:outputText value="#{car.model}" />
        </p:column>

        <p:column headerText="Year" sortBy="#{car.year}"
            filterBy="#{car.year}">
            <h:outputText value="#{car.year}" />
        </p:column>

        <p:column headerText="Manufacturer" sortBy="#{car.manufacturer}"
            filterBy="#{car.manufacturer}">
            <h:outputText value="#{car.manufacturer}" />
        </p:column>

        <p:column headerText="Color" sortBy="#{car.color}"
            filterBy="#{car.color}">
            <h:outputText value="#{car.color}" />
        </p:column>
    </p:dataTable>
</h:form>
</h:body>
</html>

TableBean.java

package com.solartis.primefaces.sample;

import java.util.ArrayList;
import java.util.List;
import java.util.UUID;

import javax.faces.bean.ManagedBean;

import org.primefaces.model.LazyDataModel;

@ManagedBean
public class TableBean {

private LazyDataModel<Car> lazyModel;

private Car selectedCar;

private List<Car> cars = new ArrayList<Car>();

private final static String[] colors;

private final static String[] manufacturers;

static {
    colors = new String[10];
    colors[0] = "Black";
    colors[1] = "White";
    colors[2] = "Green";
    colors[3] = "Red";
    colors[4] = "Blue";
    colors[5] = "Orange";
    colors[6] = "Silver";
    colors[7] = "Yellow";
    colors[8] = "Brown";
    colors[9] = "Maroon";

    manufacturers = new String[10];
    manufacturers[0] = "Mercedes";
    manufacturers[1] = "BMW";
    manufacturers[2] = "Volvo";
    manufacturers[3] = "Audi";
    manufacturers[4] = "Renault";
    manufacturers[5] = "Opel";
    manufacturers[6] = "Volkswagen";
    manufacturers[7] = "Chrysler";
    manufacturers[8] = "Ferrari";
    manufacturers[9] = "Ford";
}

public TableBean() {
    populateRandomCars(cars, 50);
    lazyModel = new LazyCarDataModel(cars);
}

public Car getSelectedCar() {
    return selectedCar;
}

public void setSelectedCar(Car selectedCar) {
    this.selectedCar = selectedCar;
}

public LazyDataModel<Car> getLazyModel() {
    return lazyModel;
}

private void populateRandomCars(List<Car> list, int size) {
    for (int i = 0; i < size; i++) {
        list.add(new Car(getRandomModel(), getRandomYear(),
                getRandomManufacturer(), getRandomColor()));
    }
}

private String getRandomColor() {
    return colors[(int) (Math.random() * 10)];
}

private String getRandomManufacturer() {
    return manufacturers[(int) (Math.random() * 10)];
}

private int getRandomYear() {
    return (int) (Math.random() * 50 + 1960);
}

private String getRandomModel() {
    return UUID.randomUUID().toString().substring(0, 8);
}
}

LazyCarDataModel.java

package com.solartis.primefaces.sample;

import java.util.ArrayList;

/**
 * Dummy implementation of LazyDataModel that uses a list to mimic a real 
   datasource like a database.
 */
public class LazyCarDataModel extends LazyDataModel<Car> {

private List<Car> datasource;

public LazyCarDataModel(List<Car> datasource) {
    this.datasource = datasource;
}

@Override
public Car getRowData(String rowKey) {
    for(Car car : datasource) {
        if(car.getModel().equals(rowKey))
            return car;
    }

    return null;
}

@Override
public void setRowIndex(int rowIndex) {

    if (rowIndex == -1 || getPageSize() == 0) {
        super.setRowIndex(-1);
    } else
        super.setRowIndex(rowIndex % getPageSize());
}

@Override
public Object getRowKey(Car car) {
    return car.getModel();
}

@Override
public List<Car> load(int first, int pageSize, 
                      List<SortMeta> multiSortMeta,Map<String, String> filters) {

    System.out.println("\nTHE INPUT PARAMETER VALUE OF LOAD METHOD :   
    \t"+"first=" + first + ", pagesize=" + pageSize + ", multiSortMeta=" + 
    multiSortMeta + " filter:" + filters);

    System.out.println("\nTHE MULTISORTMETA CONTENT  : \t");

    if (multiSortMeta != null) {
        for (SortMeta sortMeta : multiSortMeta) {
            System.out.println("SORTFIELD:" +sortMeta.getSortField());
            System.out.println("SORTORDER:" +sortMeta.getSortOrder());
                    System.out.println("SORTFUNCTION:"
                                                         +sortMeta.getSortFunction());
            System.out.println("COLUMN:" +sortMeta.getColumn());
            System.out.println("CLASS:" +sortMeta.getClass());
        }
    }

    List<Car> data = new ArrayList<Car>();

    //filter
    for(Car car : datasource) {
        boolean match = true;

        for(Iterator<String> it = filters.keySet().iterator(); it.hasNext();) {
            try {
                String filterProperty = it.next();
                String filterValue = filters.get(filterProperty);
                String fieldValue =  String.valueOf(car.getClass().
                                getField(filterProperty).get(car));

                if(filterValue == null || fieldValue.startsWith(filterValue)) {
                    match = true;
                }
                else {
                    match = false;
                    break;
                }
            } catch(Exception e) {
                match = false;
            } 
        }

        if(match) {
            data.add(car);
        }
    }


    //rowCount
    int dataSize = data.size();
    this.setRowCount(dataSize);

    //paginate
    if(dataSize > pageSize) {
        try {
            return data.subList(first, first + pageSize);
        }
        catch(IndexOutOfBoundsException e) {
            return data.subList(first, first + (dataSize % pageSize));
        }
    }
    else {
        return data;
    }
}
}

除非我对多列排序进行分页，否则load()方法带有List<SortMeta>的{{1}}方法不会向我提供当前已排序以转移到其他页面的列详细信息，这与{使用load()的{1}}方法提供了那些排序详细信息。

例如：

点击“制造商”中的排序箭头，然后按住Ctrl键并点击“年份”的排序箭头
- 你会得到String sortField, SortOrder sortOrder方法的排序列详细信息（我在load方法中打印了输入参数值）。
现在，做分页。这里load()方法未能给出排序列详细信息
- 不仅用于分页，如果在点击排序列后输入列过滤器值，则存在同样的问题

我该如何解决这个问题？

Answer 1

我暂时解决了这个问题...... 有一个sessioncoped托管bean用于存储排序列的详细信息，以便在分页期间进入load（），如： -

@ManagedBean
@SessionScoped

public class StoreSortColumnDetail implements Serializable{


    /** holds multisort values**/
private List<SortMeta> mMultiSortMeta;


public List<SortMeta> getMultiSortMeta() {
    return mMultiSortMeta;
}

public void setMultiSortMeta(List<SortMeta> multiSortMeta) {
    mMultiSortMeta = multiSortMeta;
}

public void clearMultiSortMeta() {
    if(this.mMultiSortMeta != null)
        this.mMultiSortMeta.clear();

}
}

并在load（）中使用它，如下所示：

@Override
public List<Car> load(int first, int pageSize, 
                  List<SortMeta> multiSortMeta,Map<String, String> filters) {

/** Instance to the SessionScoped scoped StoreSortColumnDetail managed bean*/
@ManagedProperty(value="#{StoreSortColumnDetail }")
private StoreSortColumnDetail storeSortColumnDetail ;

public void setStoreSortColumnDetail (StoreSortColumnDetail sortColumnDetail ) {
    this.storeSortColumnDetail = sortColumnDetail ;
}

/** to hold the handled sort column detail**/
List<SortMeta> handledMultiSortMeta = new ArrayList<SortMeta>();

/*Here starts the multisortmeta handling process*/
   /** check for List<SortMeta> for null**/
if(multiSortMeta != null ) {

    /** updates StoreSortColumnDetail's List<SortMeta> with Load()'s List<SortMeta>**/
    storeSortColumnDetail.setMultiSortMeta(multiSortMeta);
    handledMultiSortMeta  = multiSortMeta;
} 
/** check for List<SortMeta> for notnull **/
else if (multiSortMeta == null) {

    /**assigns Load()'s List<SortMeta> with StoreSortColumnDetail's List<SortMeta>**/
    handledMultiSortMeta  = storeSortColumnDetail.getMultiSortMeta();
} 


   /*Now u have handled multisortmeta from load()...
     and u can process now from handledMultiSortMeta*/
}

我希望你知道我是如何处理的，如果不是亲密的我...... 但这是一种暂时的方式，需要通过主要方式处理它...

Answer 2

虽然这种方法可以解决问题，但您可以轻松地将实际操作委托给lazyDataModel中的Primefaces。通过这样做，您可以保持代码库更清晰，因为您没有任何其他类可以运行，您将重用已经开发的组件（无论如何）。

如果您检查了PrimeFaces源代码，您将看到DataTable为其每个功能使用具体类，如过滤，排序，扩展等......对于排序Primefaces使用一个名为BeanPropertyComparator的类，此类需要确定属性到其构造函数，但大多数这些属性可以从sortMeta属性获取发送到lazyDataModel的load方法。但是，如果您想获得DataTable对象所需的所有属性，如果您知道有问题的DataTable的客户端ID，则可以从FacesContext获取该对象。

假设您在名为activeTable的变量中有数据表实例，那么您需要做的就是：

UIColumn sortColumn = sortMeta.getSortColumn()
if(sortColumn.isDynamic())
  ((DynamicColumn)sortColumn).applyStatelessModel();
//for single mode sorting
ValueExpression sortByVal = activeTable.getValueExpression("sortBy");
//multiColumn sorting 
ValueExpression sortByVal = sortColumn.getValueExpression("sortBy");
int caseSensitive = activeTable.isCaseSensitiveSort();
SortOrder order = sortMeta.getSortOrder();
MethodExpression exp = sortColumn.getSortFunction();
//pass required properties to constructor
//single mode sort
Collections.sort(filteredItems, new BeanPropertyComparator(......))
//for multi column sort use ChainedBeanPropertyComparator and add every new comparator to it than
Collections.sort(filteredItems, chainedComparator);

默认情况下，您的排序将支持任何在不牺牲安全性的情况下支持默认机制支持的功能。

<p：datatable>中的sortMode =“multiple”和lazy =“true”在分页期间清除multisort meta </p：datatable>

2 个答案: