Jasper Reports 简明教程

Report Variables

报表变量是建立在报表表达式之上的特殊对象。

Report variables are special objects built on top of the report expression.

报表变量简化了以下任务：

Report variables simplify the following tasks −

Report expressions, which are heavily used throughout the report template. These expressions can be declared only once by using the report variables.
Report variables can perform various calculations based on the corresponding expressions values such as count, sum, average, lowest, highest, variance, etc.

如果在报表设计中定义了变量，则表达式中的新变量可以引用这些变量。因此，在报表设计中声明变量的顺序很重要。

If variables are defined in a report design, then these can be referenced by new variables in the expressions. Hence, the order in which the variables are declared in a report design is important.

Variable Declaration

变量声明如下：

A variable declaration is as follows −

<variable name = "CityNumber" class = "java.lang.Integer" incrementType = "Group"
   incrementGroup = "CityGroup" calculation = "Count">
   <variableExpression>
      <![CDATA[Boolean.TRUE]]>
   </variableExpression>
</variable>

如上所见，<variable> 元素包含许多属性。这些属性总结如下：

As seen above, <variable> element contains number of attributes. These attributes are summarized below −

The Name Attribute

与参数和字段类似，</variable> 元素的 name 属性是必需的。它允许通过其在报表表达式中声明的名称引用变量。

Similar to parameters and fields, the name attribute of </variable> element is mandatory. It allows referencing the variable by its declared name in the report expressions.

The Class Attribute

class 属性也是必需的，它为变量值指定类名。其默认值为 java.lang.String。可以在报表编译时间和报表填充时间将其更改为在类路径中可用的任何类。引擎负责在报表表达式中使用 $V{} 令牌的类型转换，因此不需要手动类型转换。

The class attribute is also mandatory that specifies the class name for the variable values. Its default value is java.lang.String. This can be changed to any class available in the classpath, both at the report-compilation time and the report filling time. The engine takes care of type-casting in report expressions which the $V{} token is used, hence manual type-casting is not required.

Calculation

此属性确定——在填充报表时对变量执行什么计算。以下小节描述了 <variable> 元素的 calculation 属性的所有可能值。

This attribute determines − what calculation to perform on the variable when filling the report. The following subsections describe all the possible values for the calculation attribute of the <variable> element.

Average − The variable value is the average of every non-null value of the variable expression. Valid for numeric variables only.
Count − The variable value is the count of non-null instances of the variable expression.
First − The variable value is the value of the first instance of the variable expression. Subsequent values are ignored.
Highest − The variable value is the highest value for the variable expression.
Lowest − The variable value is the lowest value for the variable expression in the report.
Nothing − No calculations are performed on the variable.
StandardDeviation − The variable value is the standard deviation of all non-null values matching the report expression. Valid for numeric variables only.
Sum − The variable value is the sum of all non-null values returned by the report expression.
System − The variable value is a custom calculation (calculating the value for that variable yourself, using the scriptlets functionality of JasperReports).
Variance − The variable value is the variance of all non-null values returned by evaluation of the report variable’s expression.

Incrementer FactoryClass

此属性决定在报表上填写当前记录时用于计算变量值所用的类。默认值应为实施 net.sf.jasperreports.engine.fill.JRIncrementerFactory 的任何类。引擎将在运行时使用工厂类来根据变量所设置的计算属性实例化增量对象。

This attribute determines the class used to calculate the value of the variable when filling the current record on the report. Default value would be any class implementing net.sf.jasperreports.engine.fill.JRIncrementerFactory. The factory class will be used by the engine to instantiate incrementer objects at runtime depending on the calculation attribute set for the variable.

IncrementType

这决定何时重新计算变量值。此属性使用值，如下 −

This determines when to recalculate the value of the variable. This attribute uses values, as below −

Column − The variable value is recalculated at the end of each column.
Group − The variable value is recalculated when the group specified by incrementGroup changes.
None − The variable value is recalculated with every record.
Page − The variable value is recalculated at the end of every page.
Report − The variable value is recalculated once, at the end of the report.

IncrementGroup

当 incrementType 为组时，这决定在哪个组名称处重新计算变量值。此处为 JRXML 报表模板中声明的任何组之名称。

This determines the name of the group at which the variable value is recalculated, when incrementType is Group. This takes name of any group declared in the JRXML report template.

ResetType

这决定何时重置变量值。此属性使用值，如下 −

This determines when the value of a variable is reset. This attribute uses values, as below −

Column − The variable value is reset at the beginning of each column.
Group − The variable value is reset when the group specified by incrementGroup changes.
None − The variable value is never reset.
Page − The variable value is reset at the beginning of every page.
Report − The variable value is reset only once, at the beginning of the report.

ResetGroup

当 resetType 为组时，这决定在哪个组名称处重置变量值。此属性的值为 JRXML 报表模板中声明的任何组的名称。

This determines the name of the group at which the variable value is reset, when resetType is Group. The values for this attribute would be the name of any group declared in the JRXML report template.

Built-In Report Variables

有些内置系统变量随时可用于表达式中，如下 −

There are some built-in system variables, ready to use in expressions, as follows −

S.NO	Variable Name and Description
1	PAGE_NUMBER This variable’s value is its current page number. It can be used to display both the current page number and the total number of pages using a special feature of JasperReports text field elements, the evaluationTime attribute.
2	COLUMN_NUMBER This variable contains the current column number.
3	REPORT_COUNT This report variable contains the total number of records processed.
4	PAGE_COUNT This variable contains the number of records that were processed when generating the current page.
5	COLUMN_COUNT This variable contains the number of records that were processed when generating the current column.
6	GroupName_COUNT The name of this variable is derived from the name of the group it corresponds to, suffixed with the _COUNT sequence. This variable contains the number of records in the current group.

Example

让我们向现有报表模板（第 Report Designs 章）添加一个变量（ countNumber ）。我们将在每个记录之前添加计数。经修订的报表模板（jasper_report_template.jrxml）如下。将其保存到 C:\tools\jasperreports-5.0.1\test 目录中−

Let’s add a variable (countNumber) to our existing report template (Chapter Report Designs). We will prefix the count to each record. The revised report template (jasper_report_template.jrxml) is as follows. Save it to C:\tools\jasperreports-5.0.1\test directory −

<?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>

   <variable name = "countNumber" class = "java.lang.Integer" calculation = "Count">
      <variableExpression>
         <![CDATA[Boolean.TRUE]]>
      </variableExpression>
   </variable>

   <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["  " + String.valueOf($V{countNumber}) +"."+$F{name}]]>
            </textFieldExpression>
         </textField>

      </band>
   </detail>

</jasperReport>

用于填充报告的 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 -

The java codes for report filling remains unchanged. The contents of the file C:\tools\jasperreports-5.0.1\test\src\com\tutorialspoint\JasperReportFill.java are as given below −

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();
      }
   }
}

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

The contents of the POJO file C:\tools\jasperreports-5.0.1\test\src\com\tutorialspoint\DataBean.java are as given below −

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;
   }
}

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

The contents of the file C:\tools\jasperreports-5.0.1\test\src\com\tutorialspoint\DataBeanList.java are as given below −

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;
   }
}

Report Generation

我们将使用常规 ANT 构建流程编译并执行上述文件。build.xml 文件（保存在 C:\tools\jasperreports-5.0.1\test 目录下）的内容如下。

We will compile and execute the above file using our regular ANT build process. The contents of the file build.xml (saved under directory C:\tools\jasperreports-5.0.1\test) are as given below.

导入文件 - baseBuild.xml 从第 Environment Setup 章选取并应该放置在与 build.xml 相同的目录中。

The import file - baseBuild.xml is picked from the chapter Environment Setup and should be placed in the same directory as the build.xml.

<?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进入放置 build.xml 的目录。最后，执行命令 ant -Dmain-class=com.tutorialspoint.JasperReportFill （viewFullReport 是默认目标），如下所示 −

Next, let’s open command line window and go to the directory where build.xml is placed. Finally, execute the command ant -Dmain-class=com.tutorialspoint.JasperReportFill (viewFullReport is the default target) as −

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

以上编译的结果是在屏幕下方打开一个 JasperViewer 窗口−

As a result of above compilation, a JasperViewer window opens up as in the screen below −

此处，我们看到每个记录前加了计数。

Here, we see that the count is prefixed for each record.