Question

我遇到了一个问题：当我向带有字段名别名的数据库发出SQL请求时，我无法用h：dataTable（我使用JSF）显示它们。

这里的例子。请求：

SELECT 
    computers.name AS computers_name,
FROM
    computers
WHERE
    computers.id IS NOT NULL AND (computers.group_id=1);

和XHTML代码：

            <h:dataTable value="#{advancedSearchComp.computers}"  
                    var="computer" rowClasses="oddTableRow, evenTableRow"
                    headerClass="tableHeader" styleClass="table">
                <h:column>
                    <f:facet name="header">name</f:facet>
                    #{computer.computers_name}
                </h:column>
            </h:dataTable>

并且存在一个问题，因为h：column不能通过别名获取字段值，只能通过实名获取，并且它返回null。

最佳解决方案是什么？

我会感激任何提示。

更新。我所知道的所有手册只考虑了一些简单的案例“SELECT * FROM table”。

是否有一种在没有棘手方法的情况下在JSF中显示ResultSet的常用方法？

更新。我做到了：

<h:dataTable value="#{advancedSearchComp.selectedComputers}" var="computer" rowClasses="oddTableRow, evenTableRow"
                         headerClass="tableHeader" styleClass="table">
                <h:column>
                    <f:facet name="header">id</f:facet>
                    #{computer.computers_id}
                </h:column>
                <h:column>
                    <f:facet name="name">Name</f:facet>
                    #{computer.computers_name}
                </h:column>
                <h:column>
                    <f:facet name="header">Location</f:facet>
                    #{computer.locations_name}
                </h:column>
                <h:column>
                    <f:facet name="header">Rack</f:facet>
                    #{computer.racks_name}
                </h:column>
                <h:column>
                    <f:facet name="header">Rack unit</f:facet>
                    #{computer.computers_rack_unit}
                </h:column>
                <h:column>
                    <f:facet name="header">Serial</f:facet>
                    #{computer.computers_serial}
                </h:column>
                <h:column>
                    <f:facet name="header">Inv number</f:facet>
                    #{computer.computers_inv_number}
                </h:column>
                <h:column>
                    <f:facet name="header">Status</f:facet>
                    #{computer.computers_status_name}
                </h:column>
            </h:dataTable>

public List<ComputerWrapper> getSelectedComputers() throws SQLException{
    ComputerWrapper computer;
    selectedComputers.clear();
    if (query==null) {
        return null;
    }
    else {
        Statement sth=dbhIrmdb.createStatement();
        ResultSet rowSet=sth.executeQuery(query);
        while (rowSet.next()) {
            computer=new ComputerWrapper();
            computer.setComputers_id(rowSet.getString("computers_id"));
            computer.setComputers_name(rowSet.getString("computers_name"));
            computer.setLocations_name(rowSet.getString("locations_name"));
            computer.setRacks_name(rowSet.getString("racks_name"));
            computer.setComputers_rack_unit(rowSet.getString("computers_rack_unit"));
            computer.setComputers_serial(rowSet.getString("computers_serial"));
            computer.setComputers_inv_number(rowSet.getString("computers_inv_number"));
              computer.setComputers_status_name(rowSet.getString("computers_status_name"));
            selectedComputers.add(computer);
        }         
        sth.close();
        return selectedComputers;
    }

//返回null; }

公共类ComputerWrapper { private String computers_id，computers_name，locations_name，racks_name，computers_rack_unit， computers_serial，computers_inv_number，computers_status_name;

public String getComputers_id() {
    return computers_id;
}

public void setComputers_id(String computers_id) {
    this.computers_id=computers_id;
}

public String getComputers_name() {
    return computers_name;
}

public void setComputers_name(String computers_name) {
    this.computers_name=computers_name;
}

public String getLocations_name() {
    return locations_name;
}

public void setLocations_name(String locations_name) {
    this.locations_name=locations_name;
}

public String getRacks_name() {
    return racks_name;
}

public void setRacks_name(String racks_name) {
    this.racks_name=racks_name;
}

public String getComputers_rack_unit() {
    return computers_rack_unit;
}

public void setComputers_rack_unit(String computers_rack_unit) {
    this.computers_rack_unit=computers_rack_unit;
}

public String getComputers_serial() {
    return computers_serial;
}

public void setComputers_serial(String computers_serial) {
    this.computers_serial=computers_serial;
}

public String getComputers_inv_number() {
    return computers_inv_number;
}

public void setComputers_inv_number(String computers_inv_number) {
    this.computers_inv_number=computers_inv_number;
}

public String getComputers_status_name() {
    return computers_status_name;
}

public void setComputers_status_name(String computers_status_name) {
    this.computers_status_name=computers_status_name;
}

public ComputerWrapper() {
    computers_id=""; computers_name=""; locations_name=""; racks_name=""; computers_rack_unit="";
    computers_serial=""; computers_inv_number=""; computers_status_name="";
}

Answer 1

您需要创建一个班级Computer

public class Computer{
    private String computerName;
    // getter-setter
}

advancedSearchComp托管bean

@ManagedBean (name = "advancedSearchComp")
public class AdvancedSearchComp{
    private List<Computer> computers;
    // getter-setter
    // code to populate computers and map result set to the Computer bean
}

要将结果集映射到java bean，您需要迭代结果集并准备一个列表。

然后在XHTML中

<h:dataTable value="#{advancedSearchComp.computers}"  
    var="computer" rowClasses="oddTableRow, evenTableRow"
    headerClass="tableHeader" styleClass="table">
    <h:column>
          <f:facet name="header">name</f:facet>
          <h:outputText value = "#{computer.computerName}"/>
    </h:column>
</h:dataTable>

<强>更新如果要显示16个或大量字段，则有以下两个选项：

Option1 添加bean中的所有字段，然后按上面显示它们

Option2 在bean中添加地图，然后在XHTML中使用此地图。

public class Computer{
    private Map<String, Object> dataMap;
    // getter-setter
}

在XHTML上

<h:dataTable value="#{advancedSearchComp.computers}"  
    var="computer" rowClasses="oddTableRow, evenTableRow"
    headerClass="tableHeader" styleClass="table">
    <h:column>
          <f:facet name="header">name</f:facet>
          <h:outputText value = "#{computer.dataMap['computerName']}"/>
    </h:column>
    <h:column>
          <f:facet name="header">Brand</f:facet>
          <h:outputText value = "#{computer.dataMap['computerBrand']}"/>
    </h:column>
</h:dataTable>

迭代结果集以填充dataMap

ResultSet rs= statement.executeQuery();
if(rs!= null){
dataMap = new HashMap<String, Object>();
ResultSetMetaData rsmd = rs.getMetaData();
while(rs.next()){
    for(int _iterator = 0; _iterator < rsmd.getColumnCount(); _iterator++){
        String columnName = rsmd.getColumnName(_iterator + 1);
    Object columnValue = rs.getObject(_iterator + 1);
        dataMap.put(columnName , columnValue );
    }
}
}

Answer 2

无法通过别名获取它。你必须将它分配给bean中某个地方的实际对象。如果尚未创建专门用于存储ResultSet结果的对象，请执行此操作，将其传递到页面并显示。

将名称包装在outputText标记周围也很有帮助，比如

<h:outputText value="#{computer.computersName}" />

Answer 3

如果computers中的advancedSearchComp属性属于ResultSet类型，那么您应该能够编写如下内容：

<h:dataTable value="#{advancedSearchComp.computers}" var="computer">
  <h:column>
    <f:facet name="header">name</f:facet>
    <h:outputText value="#{computer.getString('computers_name')}" />
  </h:column>
</h:dataTable>

如何通过别名获取字段值，而不是JSF中的名称？

3 个答案: