Jasper Reports 简明教程
Report Expression
报表表达式是 JasperReports 的强大功能,它允许我们在报表上显示计算数据。计算数据不是静态数据,也没有特别作为报表参数或数据源字段传递。报表表达式由报表参数、字段和静态数据组合而成。默认情况下,Java 语言用于编写报表表达式。JasperReports 编译器支持用于报表表达式的其他脚本语言,如 Groovy 脚本语言、JavaScript 或 BeanShell 脚本。
本章将为您解释报表表达式如何工作,假设报表表达式仅使用 Java 语言编写。在一个 JRXML 报表模板中,有若干元素定义表达式,如下 −
-
<variableExpression>
-
<initialValueExpression>
-
<groupExpression>
-
<printWhenExpression>
-
<imageExpression>
-
<textFieldExpression>
Expression Declaration
基本上,所有报表表达式都是 Java 表达式,可以引用报表字段、报表变量和报表参数。
Field Reference in Expression
要在表达式中使用报表字段引用,必须将字段的名称放在 $F{*and }* 字符序列之间,如下所示 −
<textfieldexpression>
$F{Name}
</textfieldexpression>
以下是现有 JRXML 文件中的一段代码(第 Report Designs) 章 −
<textFieldExpression class = "java.lang.String">
<![CDATA[$F{country}]]>
</textFieldExpression>
Variable Reference in Expression
要在表达式中引用变量,必须将变量名称放在 $V{*and }* 之间,如下面给出的示例所示 −
<textfieldexpression>
"Total height : " + $V{SumOfHeight} + " ft."
</textfieldexpression>
Parameter Reference in Expression
要在表达式中引用参数,应该将参数名称放在 $P{*and }* 之间,如下面给出的示例所示 −
<textfieldexpression>
"ReportTitle : " + $P{Title}
</textfieldexpression>
以下是现有 JRXML 文件中的一段代码,它说明了如何在表达式中引用参数。(第 Report Designs 章的 JRXML) −
<textField isBlankWhenNull = "true" bookmarkLevel = "1">
<reportElement x = "0" y = "10" width = "515" height = "30"/>
<textElement textAlignment = "Center">
<font size = "22"/>
</textElement>
<textFieldExpression class = "java.lang.String">
<![CDATA[$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>
如您在上面看到的那样,参数、字段和变量引用实际上是真正的 Java 对象。通过在报表模板中进行参数、字段或变量声明了解它们的类,我们甚至可以在表达式中对那些对象引用调用方法。
以下示例显示了如何从 java.lang.String 报表字段“Name”中提取并显示第一个字母 −
<textFieldExpression>
$F{Name}.substring(0, 1)
</textFieldExpression>
Resource Bundle Reference in Expression
要在表达式中引用资源,应将键放在 $R{*and }* 之间,如下面给出的示例所示 −
<textfieldexpression>
$R{report.title}
</textfieldexpression>
基于运行时提供的语言环境和 report.title 键,加载与报表模板关联的资源包。因此,通过从资源包中提取 String 值来显示报表标题。关于国际化的更多信息可以在第 Internationalization 章中找到。
Calculator
计算器是 JasperReports 中的一个实体,它在报告填充时评估表达式并增加变量或数据集。在编译过程中,编译器将生成信息并将其存储在编译报告中。在报告填充时,使用此信息来构建 net.sf.jasperreports.engine.fill.JRCalculator 类的实例。
Java 源文件由基于 Java 的报告编译器动态生成和编译。这个生成的类是 JRCalculator 的子类,编译生成字节码存储在 JasperReport 对象中。在报告填充时加载这个字节码,并实例化结果类以获取表达式评估所需的计算器对象。
Conditional Expressions
定义变量表达式时,JasperReports 不支持 if-else 语句。相反,可以使用三元运算符 {cond} ? {statement 1} : {statement 2} 。此运算符可以嵌套在 Java 表达式中,以根据多种条件获取所需输出。
Example of conditional Expression in Report
让我们修改现有的报告模板(第 Report Designs 章),并为 country 字段添加条件表达式。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 目录中−
<?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}.isEmpty() ? "NO COUNTRY" : $F{country}]]>
</textFieldExpression>
</textField>
<textField>
<reportElement x = "0" y = "0" width = "136" height = "15" />
<textElement textAlignment = "Center" verticalAlignment = "Middle" />
<textFieldExpression class = "java.lang.String">
<![CDATA[$F{name}]]>
</textFieldExpression>
</textField>
</band>
</detail>
</jasperReport>
报告填充的 Java 代码如下。文件 C:\tools\jasperreports-5.0.1\test\src\com\tutorialspoint\JasperReportFill.java 的内容为 −
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 的内容为 -
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;
}
}
我们会在 Java Bean List 中添加一条新记录,country 字段为空。文件 C:\tools\jasperreports-5.0.1\test\src\com\tutorialspoint\DataBeanList.java 的内容为 −
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"));
dataBeanList.add(produce("Tanmay", ""));
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
我们使用常规 ANT 构建进程编译并执行上述文件。build.xml 文件(保存在目录 C:\tools\jasperreports-5.0.1\test 下)的内容如下。
导入文件 - baseBuild.xml 取自第 Environment Setup ,应放在与 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,打开命令行窗口,并转到放置 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:
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 3 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: 5 minutes 5 seconds
C:\tools\jasperreports-5.0.1\test>
作为上述编译的结果,一个 JasperViewer 窗口会打开,如以下给出的屏幕截图所示 -
在这里,我们可以看到,对于最后一条记录,我们没有传递 country 字段的任何数据,“NO COUNTRY” 正在打印。