报告组

JasperReports 中的组有助于以逻辑方式组织报表上的数据。报表组表示数据源中的一系列连续记录，这些记录具有一些共同点，例如某些报表字段的值。报告组由 <group> 元素定义。一个报告可以有任意数量的组。一旦宣布，团体就可以在整个报告中被提及。

报告组具有三个要素 -

组表达式- 这表示必须更改才能开始新数据组的数据。
组标题部分- 帮助将标签放置在分组数据的开头。
组页脚部分- 帮助将标签放置在分组数据的末尾。

在报告填充时对数据源进行迭代期间，如果组表达式的值发生更改，则会发生组破裂，并且相应的 <groupFooter> 和 <groupHeader> 部分将插入到结果文档中。

报表组机制不对数据源提供的数据执行任何排序。仅当数据源中的记录已根据报表中使用的组表达式进行排序时，数据分组才会按预期工作。

群组属性

<group> 元素包含允许我们控制分组数据的布局方式的属性。属性总结如下表 -

序号	属性和描述
1	姓名这是强制性的。它按名称引用报表表达式中的组。它遵循我们提到的报告参数、字段和报告变量的相同命名约定。当您想要引用特定的报告组时，它可以在其他 JRXML 属性中使用。
2	是开始新列当设置为true时，每个数据组都将从一个新列开始。默认值为false。
3	是开始新页当设置为true时，每个数据组都将在新页面上开始。默认值为false。
4	重置页码当设置为true时，每次新组启动时都会重置报告页码。默认值为false。
5	isReprintHeaderOnEachPage 当设置为true时，组标题将在每一页上重新打印。默认值为false。
6	开始新页面的最小高度定义列底部所需的最小垂直空间量，以便将组标题放置在当前列上。金额以报告单位指定。
7	页脚位置呈现页面上组页脚的位置，以及其与后面的报表部分相关的Behave。其值可以是：Normal、StackAtBottom、ForceAtBottom和CollateAtBottom。默认值为正常。
8	保持在一起当设置为true时，可防止组在第一次尝试中断时分裂。

例子

让我们向现有报告模板添加一个组 ( CountryGroup )（第 1 章报告设计）。对每个国家/地区的出现次数进行计数，并将计数显示为组页脚。在组头中，每条记录的计数都带有前缀。修改后的报告模板（jasper_report_template.jrxml）如下。将其保存到 C:\tools\jasperreports-5.0.1\test 目录 -

<?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"/>
   
   <variable name = "CountryNumber" class = "java.lang.Integer"
      incrementType = "Group" incrementGroup = "CountryGroup"
      calculation = "Count">
      <variableExpression><![CDATA[Boolean.TRUE]]></variableExpression>
   </variable>
   
   <group name = "CountryGroup" minHeightToStartNewPage = "60">
      <groupExpression><![CDATA[$F{country}]]></groupExpression>
      
      <groupHeader>
         <band height = "20">
            
            <textField evaluationTime = "Group" evaluationGroup = "CountryGroup"
               bookmarkLevel = "1">
               <reportElement mode = "Opaque" x = "0" y = "5" width = "515"
                  height = "15" backcolor = "#C0C0C0"/>
               
               <box leftPadding = "10">
                  <bottomPen lineWidth = "1.0"/>
               </box>
               <textElement/>
               
               <textFieldExpression class = "java.lang.String">
                  <![CDATA["  " + String.valueOf($V{CountryNumber}) + ". "
                  + String.valueOf($F{country})]]>
               </textFieldExpression>
               
               <anchorNameExpression>
                  <![CDATA[String.valueOf($F{country})]]>
               </anchorNameExpression>
            </textField>
         
         </band>
      </groupHeader>
      
      <groupFooter>
         <band height = "20">
            
            <staticText>
               <reportElement x = "400" y = "1" width = "60" height = "15"/>
               <textElement textAlignment = "Right"/>
               <text><![CDATA[Count :]]></text>
            </staticText>
            
            <textField>
               <reportElement x = "460" y = "1" width = "30" height = "15"/>
               <textElement textAlignment = "Right"/>
               
               <textFieldExpression class = "java.lang.Integer">
                  <![CDATA[$V{CountryGroup_COUNT}]]>
               </textFieldExpression>
            </textField>
         
         </band>
      </groupFooter>
   
   </group>
   
   <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>

报告填写的java代码保持不变。文件C:\tools\jasperreports-5.0.1\test\src\com\tutorialspoint\JasperReportFill.java的内容如下 -

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 文件C:\tools\jasperreports-5.0.1\test\src\com\tutorialspoint\DataBean.java的内容如下 -

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;
   }
}

文件C:\tools\jasperreports-5.0.1\test\src\com\tutorialspoint\DataBeanList.java的内容如下 -

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;
   }
}

报告生成

我们将使用常规 ANT 构建过程来编译并执行上述文件。文件 build.xml（保存在目录 C:\tools\jasperreports-5.0.1\test 下）的内容如下。

导入文件 - baseBuild.xml 从“环境设置”一章中选取，应放置在与 build.xml 相同的目录中。

<?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>

接下来，我们打开命令行窗口并进入build.xml所在的目录。最后，执行命令ant -Dmain-class=com.tutorialspoint.JasperReportFill（viewFullReport 是默认目标）：

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

作为上述编译的结果，JasperViewer 窗口将打开，如下面的屏幕所示 -

在这里，我们看到每个国家/地区都进行了分组，每个国家/地区的出现次数显示在每个组的页脚处。