JasperReports - 编译报表设计

我们在上一章节生成了 JasperReport 模板（JRXML 文件）。此文件不能直接用于生成报表。它必须编译成 JasperReport 的原生二进制格式，称为 **Jasper** 文件。编译时，我们将 JasperDesign 对象转换为 JasperReport 对象：

接口 net.sf.jasperreports.engine.design.JRCompiler 在编译过程中起着核心作用。此接口有多个实现，具体取决于报表表达式使用的语言，报表表达式可以用 Java、Groovy、JavaScript 或任何其他脚本语言编写，只要编译器实现能够在运行时对其进行评估。

我们可以通过以下两种方式编译 JRXML 文件：

编程编译。
通过 ANT 任务编译。

JRXML 的编程编译

JasperReports API 提供了一个外观类 net.sf.jasperreports.engine.JasperCompileManager 用于编译 JasperReport。此类包含多个公共静态方法，用于编译报表模板。模板的来源可以是文件、输入流和/或内存对象。

JRXML 文件 (jasper_report_template.jrxml) 的内容如下所示。它保存在 **C:\tools\jasperreports-5.0.1\test** 目录下：

<?xml version = "1.0" encoding = "UTF-8"?>
<!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" language = "groovy" pageWidth = "595"
   pageHeight = "842" columnWidth = "555" leftMargin = "20" rightMargin = "20"
   topMargin = "20" bottomMargin = "20">

   <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>
   
   <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>

以下代码演示了如何编译上述 jasper_report_template.jrxml 文件。

package com.tutorialspoint;

import net.sf.jasperreports.engine.JRException;
import net.sf.jasperreports.engine.JasperCompileManager;

public class JasperReportCompile {

   public static void main(String[] args) {
      String sourceFileName = "C://tools/jasperreports-5.0.1/test" + 
         "/jasper_report_template.jrxml";

      System.out.println("Compiling Report Design ...");
      try {
          /**
          * Compile the report to a file name same as
          * the JRXML file name
          */
         JasperCompileManager.compileReportToFile(sourceFileName);
      } catch (JRException e) {
         e.printStackTrace();
      }
      System.out.println("Done compiling!!! ...");
   }
}

模板编译

下一步，让我们将上述内容保存到文件 **C:\tools\jasperreports-5.0.1\test\src\com\tutorialspoint\JasperReportCompile.java** 中，并在 build.xml 文件中导入 baseBuild.xml，如下所示。baseBuild.xml 已经包含了 **compile** 和 **run** 目标：

<?xml version = "1.0" encoding = "UTF-8"?>
<project name = "JasperReportTest" default = "run" basedir = ".">

   <import file = "baseBuild.xml"/>

</project>

接下来，让我们打开命令行窗口，并转到放置 build.xml 的目录。最后，执行命令 **ant -Dmain-class=com.tutorialspoint.JasperReportCompile**，如下所示：

C:\tools\jasperreports-5.0.1\test>ant -Dmain-class = com.tutorialspoint.JasperReportCompile
Buildfile: C:\tools\jasperreports-5.0.1\test\build.xml
compile:
   [javac] C:\tools\jasperreports-5.0.1\test\baseBuild.xml:27:
   warning: 'includeantruntime' was not set, defaulting to
   build.sysclasspath=last;set to false for repeatable builds
   [javac] Compiling 1 source file to C:\tools\jasperreports-5.0.1\test\classes

run:
   [echo] Runnin class : com.tutorialspoint.JasperReportCompile
   [java] Compiling Report Design ...
   [java] log4j:WARN No appenders could be found for logger
   (net.sf.jasperreports.engine.xml.JRXmlDigesterFactory).
   [java] log4j:WARN Please initialize the log4j system properly.
   [java] Done compiling!!! ...

BUILD SUCCESSFUL
Total time: 8 seconds

上述编译的结果是，您将看到模板文件 jasper_report_template.jasper 已在 C:\tools\jasperreports-5.0.1\test 目录中生成。

预览已编译的报表模板

net.sf.jasperreports.view.JasperDesignViewer 可用于预览已编译的报表模板和 JRXML 模板。

为了进一步操作，让我们向上面的 build.xml 文件添加一个新的目标 **viewDesign**，这将允许我们预览已编译的报表。以下是修改后的 build.xml：

导入文件 - baseBuild.xml 来自章节环境设置，应将其放置在与 build.xml 相同的目录中。

<?xml version = "1.0" encoding = "UTF-8"?>
<project name = "JasperReportTest" default = "viewDesign" basedir = ".">

   <import file = "baseBuild.xml" />
   <target name = "viewDesign" description="Design viewer is launched 
      to preview the compiled report design.">
      
      <java classname = "net.sf.jasperreports.view.JasperDesignViewer" fork = "true">
         <arg value = "-F${file.name}.jasper" />
         <classpath refid = "classpath" />
      </java>
   </target>

</project>

让我们在命令提示符下执行命令 - **ant** (viewDesign 是默认目标)。JasperDesignViewer 窗口将打开，显示如下所示的 Jasper 文件：

通过 ANT 任务编译

由于报表模板编译更像是一个设计时作业而不是运行时作业，因此 JasperReport 库具有一个自定义 ANT 任务。在某些情况下，当 JRXML 文件在运行时创建时，我们不能使用此 ANT 任务。自定义 ANT 任务称为 JRC，由类 net.sf.jasperreports.ant.JRAntCompileTask 实现。其语法和行为与内置的 **<javac>** ANT 任务非常相似。

模板编译

让我们向现有的 build.xml 添加新的目标 **compilereportdesing**。在这里，源文件夹使用嵌套的 <src> 标记和文件集指定。嵌套的 source 标记允许编译散布在许多不同位置且未分组在单个根报表源文件夹下的报表模板。以下是修改后的 build.xml：

<?xml version = "1.0" encoding = "UTF-8"?>
<project name = "JasperReportTest" default = "compilereportdesing" basedir = ".">
   
   <import file = "baseBuild.xml" />
   <target name = "viewDesign" description = "Design viewer is 
      launched to preview the compiled report design.">
      
      <java classname = "net.sf.jasperreports.view.JasperDesignViewer" fork = "true">
         <arg value = "-F${file.name}.jasper" />
         <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，让我们打开命令提示符并转到放置 build.xml 的目录。执行命令 **ant** (compilereportdesing 是默认目标)；输出如下所示：

C:\tools\jasperreports-5.0.1\test>ant
Buildfile: C:\tools\jasperreports-5.0.1\test\build.xml

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
   https://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.

BUILD SUCCESSFUL
Total time: 5 seconds

文件 jasper_report_template.jasper 在文件系统中生成（在本例中为 C:\tools\jasperreports-5.0.1\test 目录）。此文件与通过调用 net.sf.jasperreports.engine.JasperCompileManager.compileReportToFile() 以编程方式生成的文件相同。我们可以预览此 jasper 文件，执行 **ant viewDesign**。

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