JasperReports - Fields( Fields)

报告字段是元素，表示数据源和报告模板之间的数据映射。可以在报表表达式中组合字段以获取所需的输出。报告模板可以包含零个或多个元素。声明报告字段时，数据源应提供与报告模板中定义的所有字段对应的数据。

实地宣言

现场声明如下所示 -

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

名称属性

“field”元素的name属性是必需的。它按名称引用报表表达式中的字段。

类属性

class属性指定字段值的类名。它的默认值是java.lang.String 。这可以更改为运行时可用的任何类。无论报告字段的类型如何，引擎都会在使用$ F {}标记的报表表达式中进行转换，因此无需手动转换。

字段描述

元素是可选元素。这在实现自定义数据源时非常有用。例如，我们可以存储密钥或一些信息，通过这些信息，我们可以在运行时从自定义数据源中检索字段的值。通过使用元素而不是字段名称，可以在从数据源检索字段值时轻松克服字段命名约定的限制。

以下是我们现有JRXML文件（章节报告设计）中的一段代码。在这里，我们可以看到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>

排序字段

在需要数据排序且数据源实现不支持它的时候（例如CSV数据源），JasperReports支持基于内存的基于字段的数据源排序。可以使用报告模板中的一个或多个元素完成排序。

如果指定了至少一个排序字段，则在报告填充过程中，数据源将传递给JRSortableDataSource实例。这反过来，从数据源获取所有记录，根据指定的字段执行内存排序，并替换原始数据源。

排序字段名称应与报告字段名称相同。用于排序的字段应具有实现java.util.Comparable的类型。对除java.lang.String类型之外的所有字段执行自然顺序排序（对于String类型，使用与报表填充区域设置对应的collator）。如果指定了多个排序字段，则将使用字段作为排序键，按照它们在报告模板中的显示顺序执行排序。以下示例演示了排序功能。

排序报告示例

让我们将< sortField “元素添加到现有的报告模板（章节报告设计）。让我们按降序对字段country进行排序。修订后的报告模板（jasper_report_template.jrxml）如下所示。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"/>
   <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>

报告填充的java代码保持不变。文件C:\tools\jasperreports-5.0.1\test\src\com\iowiki\JasperReportFill.java的内容如下所示 -

package com.iowiki;
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\iowiki\DataBean.java的内容如下所示 -

package com.iowiki;
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\iowiki\DataBeanList.java的内容如下所示 -

package com.iowiki;
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

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

导入文件 - baseBuild.xml是从环境设置一章中挑选出来的，应该与build.xml放在同一目录中。

<?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，让我们打开命令行窗口并转到build.xml所在的目录。最后，执行命令ant -Dmain-class=com.iowiki.JasperReportFill （viewFullReport是默认目标），如下所示 -

C:\tools\jasperreports-5.0.1\test>ant -Dmain-class=com.iowiki.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.iowiki.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窗口打开，如下面的屏幕所示 -

在这里，我们可以看到国家/地区名称按字母顺序按降序排列。

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JasperReports - 教程

JasperReports - 入门( Getting Started)

JasperReports - 环境设置( Environment Setup)

JasperReports - 生命周期( Life Cycle)

JasperReports - 设计( Designs)

JasperReports - 编译设计( Compiling Design)

JasperReports - 填充物( Fillings)

JasperReports - 查看和打印( View & Print)

JasperReports - 出口( Exporting)

JasperReports - 参数( Parameters)

JasperReports - 数据源( Data Sources)