報表欄位

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報表欄位是元素，它表示資料來源和報表模板之間資料的對映。欄位可以在報表表示式中組合以獲得所需輸出。報表模板可以包含零個或多個<field>元素。宣告報表欄位時，資料來源應提供與報表模板中定義的所有欄位相對應的資料。

欄位宣告

欄位宣告如下所示：

<field name = "FieldName" class = "java.lang.String"/>

名稱屬性

<field>元素的name屬性是必需的。它透過名稱在報表表示式中引用欄位。

類屬性

class屬性指定欄位值的類名。其預設值為java.lang.String。這可以更改為執行時可用的任何類。無論報表欄位的型別如何，引擎都會處理報表表示式中使用$F{}標記的強制轉換，因此無需手動強制轉換。

欄位描述

<fieldDesciption>元素是一個可選元素。在實現自定義資料來源時，這非常有用。例如，我們可以儲存一個鍵或一些資訊，透過這些資訊，我們可以在執行時從自定義資料來源檢索欄位的值。透過使用<fieldDesciption>元素而不是欄位名，您可以輕鬆克服在從資料來源檢索欄位值時的欄位命名約定限制。

以下是我們現有 JRXML 檔案（第 報表設計 章）中的一段程式碼。在這裡，我們可以看到name、class和fieldDescription元素的用法。

<field name = "country" class = "java.lang.String">
   <fieldDescription><![CDATA[country]]></fieldDescription>
</field>

<field name = "name" class = "java.lang.String">
   <fieldDescription><![CDATA[name]]></fieldDescription>
</field>

排序欄位

在需要資料排序並且資料來源實現不支援排序的情況下（例如 CSV 資料來源），JasperReports 支援基於記憶體的欄位資料來源排序。可以使用報表模板中的一個或多個<sortField>元素進行排序。

如果至少指定了一個排序欄位，則在報表填充過程中，資料來源將傳遞給JRSortableDataSource例項。這反過來會從資料來源中獲取所有記錄，根據指定的欄位進行記憶體排序，並替換原始資料來源。

排序欄位名應與報表欄位名相同。用於排序的欄位應該具有實現java.util.Comparable的型別。除了java.lang.String型別（對於String型別，使用與報表填充區域設定對應的校對器）之外，所有欄位都執行自然順序排序。當指定多個排序欄位時，排序將使用欄位作為排序鍵，按照它們在報表模板中出現的順序進行排序。以下示例演示了排序功能。

排序報表示例

讓我們將<sortField>元素新增到我們現有的報表模板中（第 報表設計 章）。讓我們按降序排列country欄位。修改後的報表模板 (jasper_report_template.jrxml) 如下所示。將其儲存到 C:\tools\jasperreports-5.0.1\test 目錄：

<?xml version = "1.0"?>
<!DOCTYPE jasperReport PUBLIC
   "//JasperReports//DTD Report Design//EN"
   "http://jasperreports.sourceforge.net/dtds/jasperreport.dtd">

<jasperReport xmlns = "http://jasperreports.sourceforge.net/jasperreports" xmlns:xsi = 
   "http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation = 
   "http://jasperreports.sourceforge.net/jasperreports
   http://jasperreports.sourceforge.net/xsd/jasperreport.xsd" 
   name = "jasper_report_template" pageWidth = "595" pageHeight = "842" 
   columnWidth = "515" leftMargin = "40" rightMargin = "40" 
   topMargin = "50" bottomMargin = "50">
	
   <parameter name = "ReportTitle" class = "java.lang.String"/>
   <parameter name = "Author" class = "java.lang.String"/>
   
   <queryString>
      <![CDATA[]]>
   </queryString>
   
   <field name = "country" class = "java.lang.String">
      <fieldDescription><![CDATA[country]]></fieldDescription>
   </field>
   
   <field name = "name" class = "java.lang.String">
      <fieldDescription><![CDATA[name]]></fieldDescription>
   </field>
  
   <sortField name = "country" order = "Descending"/>
   <sortField name = "name"/>
   
   <title>
      <band height = "70">
         
         <line>
            <reportElement x = "0" y = "0" width = "515" height = "1"/>
         </line>
         
         <textField isBlankWhenNull = "true" bookmarkLevel = "1">
            <reportElement x = "0" y = "10" width = "515" height = "30"/>
            
            <textElement textAlignment = "Center">
               <font size = "22"/>
            </textElement>
            
            <textFieldExpression class = "java.lang.String">
               <![CDATA[$P{ReportTitle}]]>
            </textFieldExpression>
            
            <anchorNameExpression>
               <![CDATA["Title"]]>
            </anchorNameExpression>
         </textField>
            
         <textField isBlankWhenNull = "true">
            <reportElement  x = "0" y = "40" width = "515" height = "20"/>
            
            <textElement textAlignment = "Center">
               <font size = "10"/>
            </textElement>
            
            <textFieldExpression class = "java.lang.String">
               <![CDATA[$P{Author}]]>
            </textFieldExpression>
            
         </textField>
      
      </band>
   </title>

   <columnHeader>
      <band height = "23">
         
         <staticText>
            <reportElement mode = "Opaque" x = "0" y = "3" width = "535" height = "15"
               backcolor = "#70A9A9" />
            
            <box>
               <bottomPen lineWidth = "1.0" lineColor = "#CCCCCC" />
            </box>
            
            <textElement />
				
            <text>
               <![CDATA[]]>
            </text>
         </staticText>
         
         <staticText>
            <reportElement x = "414" y = "3" width = "121" height = "15" />
            
            <textElement textAlignment = "Center" verticalAlignment = "Middle">
               <font isBold = "true" />
            </textElement>
            
            <text><![CDATA[Country]]></text>
         </staticText>
         
         <staticText>
            <reportElement x = "0" y = "3" width = "136" height = "15" />
            
            <textElement textAlignment = "Center" verticalAlignment = "Middle">
               <font isBold = "true" />
            </textElement>
            
            <text><![CDATA[Name]]></text>
         </staticText>
      
      </band>
   </columnHeader>
  
   <detail>
      <band height = "16">
         
         <staticText>
            <reportElement mode = "Opaque" x = "0" y = "0" width = "535" height = "14"
               backcolor = "#E5ECF9" />
            
            <box>
               <bottomPen lineWidth = "0.25" lineColor = "#CCCCCC" />
            </box>
				
            <textElement />
				
            <text>
               <![CDATA[]]>
            </text>
         </staticText>
         
         <textField>
            <reportElement x = "414" y = "0" width = "121" height = "15" />
            
            <textElement textAlignment = "Center" verticalAlignment = "Middle">
               <font size = "9" />
            </textElement>
            
            <textFieldExpression class = "java.lang.String">
               <![CDATA[$F{country}]]>
            </textFieldExpression>
         </textField>
         
         <textField>
            <reportElement x = "0" y = "0" width = "136" height = "15" />
            <textElement textAlignment = "Center" verticalAlignment = "Middle" />
            
            <textFieldExpression class = "java.lang.String">
               <![CDATA[$F{name}]]>
            </textFieldExpression>
         </textField>
      
      </band>
   </detail>

</jasperReport>

報表填充的Java程式碼保持不變。檔案C:\tools\jasperreports-5.0.1\test\src\com\tutorialspoint\JasperReportFill.java的內容如下：

package com.tutorialspoint;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

import net.sf.jasperreports.engine.JRException;
import net.sf.jasperreports.engine.JasperFillManager;
import net.sf.jasperreports.engine.data.JRBeanCollectionDataSource;

public class JasperReportFill {
   @SuppressWarnings("unchecked")
   public static void main(String[] args) {
      String sourceFileName =
      "C://tools/jasperreports-5.0.1/test/jasper_report_template.jasper";

      DataBeanList DataBeanList = new DataBeanList();
      ArrayList<DataBean> dataList = DataBeanList.getDataBeanList();

      JRBeanCollectionDataSource beanColDataSource =
      new JRBeanCollectionDataSource(dataList);

      Map parameters = new HashMap();
      /**
       * Passing ReportTitle and Author as parameters
       */
      parameters.put("ReportTitle", "List of Contacts");
      parameters.put("Author", "Prepared By Manisha");

      try {
         JasperFillManager.fillReportToFile(
         sourceFileName, parameters, beanColDataSource);
      } catch (JRException e) {
         e.printStackTrace();
      }
   }
}

POJO 檔案C:\tools\jasperreports-5.0.1\test\src\com\tutorialspoint\DataBean.java的內容如下：

package com.tutorialspoint;

public class DataBean {
   private String name;
   private String country;

   public String getName() {
      return name;
   }

   public void setName(String name) {
      this.name = name;
   }

   public String getCountry() {
      return country;
   }

   public void setCountry(String country) {
      this.country = country;
   }
}

檔案C:\tools\jasperreports-5.0.1\test\src\com\tutorialspoint\DataBeanList.java的內容如下：

package com.tutorialspoint;

import java.util.ArrayList;

public class DataBeanList {
   public ArrayList<DataBean> getDataBeanList() {
      ArrayList<DataBean> dataBeanList = new ArrayList<DataBean>();

      dataBeanList.add(produce("Manisha", "India"));
      dataBeanList.add(produce("Dennis Ritchie", "USA"));
      dataBeanList.add(produce("V.Anand", "India"));
      dataBeanList.add(produce("Shrinath", "California"));

      return dataBeanList;
   }

   /**
    * This method returns a DataBean object,
    * with name and country set in it.
    */
   private DataBean produce(String name, String country) {
      DataBean dataBean = new DataBean();
      dataBean.setName(name);
      dataBean.setCountry(country);
      
      return dataBean;
   }
}

報表生成

我們將使用常規的 ANT 構建過程編譯並執行上述檔案。檔案 build.xml（儲存在目錄 C:\tools\jasperreports-5.0.1\test 下）的內容如下所示。

匯入檔案 - baseBuild.xml 從第 環境設定 章中提取，應與 build.xml 放在同一目錄下。

<?xml version = "1.0" encoding = "UTF-8"?>
<project name = "JasperReportTest" default = "viewFillReport" basedir = ".">
   <import file = "baseBuild.xml" />
   
   <target name = "viewFillReport" depends = "compile,compilereportdesing,run"
      description = "Launches the report viewer to preview
      the report stored in the .JRprint file.">
      
      <java classname = "net.sf.jasperreports.view.JasperViewer" fork = "true">
         <arg value = "-F${file.name}.JRprint" />
         <classpath refid = "classpath" />
      </java>
   </target>
   
   <target name = "compilereportdesing" description = "Compiles the JXML file and
      produces the .jasper file.">
      
      <taskdef name = "jrc" classname = "net.sf.jasperreports.ant.JRAntCompileTask">
         <classpath refid = "classpath" />
      </taskdef>
      
      <jrc destdir = ".">
         <src>
            <fileset dir = ".">
               <include name = "*.jrxml" />
            </fileset>
         </src>
         <classpath refid = "classpath" />
      </jrc>
		
   </target>
	
</project>

接下來，讓我們開啟命令列視窗並轉到放置 build.xml 的目錄。最後，執行命令ant -Dmain-class=com.tutorialspoint.JasperReportFill（viewFullReport 是預設目標）如下：

C:\tools\jasperreports-5.0.1\test>ant -Dmain-class=com.tutorialspoint.JasperReportFill
Buildfile: C:\tools\jasperreports-5.0.1\test\build.xml

clean-sample:
   [delete] Deleting directory C:\tools\jasperreports-5.0.1\test\classes
   [delete] Deleting: C:\tools\jasperreports-5.0.1\test\jasper_report_template.jasper
   [delete] Deleting: C:\tools\jasperreports-5.0.1\test\jasper_report_template.jrprint

compile:
   [mkdir] Created dir: C:\tools\jasperreports-5.0.1\test\classes
   [javac] C:\tools\jasperreports-5.0.1\test\baseBuild.xml:28: warning:
   'includeantruntime' was not set, defaulting to build.sysclasspath=last;
   set to false for repeatable builds
   [javac] Compiling 7 source files to C:\tools\jasperreports-5.0.1\test\classes

compilereportdesing:
   [jrc] Compiling 1 report design files.
   [jrc] log4j:WARN No appenders could be found for logger
   (net.sf.jasperreports.engine.xml.JRXmlDigesterFactory).
   [jrc] log4j:WARN Please initialize the log4j system properly.
   [jrc] log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig
   for more info.
   [jrc] File : C:\tools\jasperreports-5.0.1\test\jasper_report_template.jrxml ... OK.

run:
   [echo] Runnin class : com.tutorialspoint.JasperReportFill
   [java] log4j:WARN No appenders could be found for logger
   (net.sf.jasperreports.extensions.ExtensionsEnvironment).
   [java] log4j:WARN Please initialize the log4j system properly.

viewFillReport:
   [java] log4j:WARN No appenders could be found for logger
   (net.sf.jasperreports.extensions.ExtensionsEnvironment).
   [java] log4j:WARN Please initialize the log4j system properly.

BUILD SUCCESSFUL
Total time: 18 seconds

上述編譯的結果是開啟一個 JasperViewer 視窗，如下圖所示：

Jasper Report Field Sort Example

在這裡，我們可以看到國家名稱按字母順序降序排列。

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