JasperReports终极指南

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"深入理解JasperReports终极指南" 《The JasperReports Ultimate Guide》是关于JasperReports的一款详尽的参考资料，由作者Teodor Danciu创作并持有版权。这本书旨在为读者提供全面的理解和实践指导，涵盖了JasperReports的各个方面，从基础到高级应用。在介绍部分，作者可能对JasperReports的基本概念、它在业务报告和数据分析中的作用以及为何选择JasperReports作为报告生成工具进行了阐述。这部分将帮助新手快速了解JasperReports的背景和价值。接下来的API概述章节，可能会深入讨论JasperReports的编程接口（API），包括主要类和方法，以及如何通过编程方式与JasperReports进行交互。这对于开发者来说至关重要，因为他们需要利用这些API来创建、编译和运行报告。主要任务和过程章节是本书的核心，列举了使用JasperReports时的关键步骤。其中： 1. XML解析：JasperReports设计报告通常基于XML格式，这一部分可能会讲解如何解析这些XML文件以获取报告布局和数据定义。 2. 编译报告设计：解释了如何将XML设计转化为可执行的JasperReport对象，这涉及到编译过程和JasperCompileManager的使用。 3. 报告设计预览：讨论了在实际填充数据之前如何查看和调试报告设计，可能包括JasperDesignViewer等工具的使用。 4. 填充报告：详细介绍了如何将数据源（如数据库、CSV文件等）与报告模板结合，生成动态报告，涉及JasperFillManager和JRDataSource。 5. 查看报告：讲述了在Java Swing、Web应用或其他环境中展示报告的方法，以及JasperViewer的使用。 6. 打印报告：可能包括如何将生成的报告发送到打印机，以及配置打印选项的细节。 7. 导出报告：这部分将涵盖各种导出格式（如PDF、Excel、HTML等），以及JasperExportManager的功能。 8. 对象加载和保存：讨论了如何保存和加载JasperReport对象，以便在不同时间或环境中重用报告设计。第4章以后的内容可能继续深入到更具体的特性，如样式和格式设置、图表创建、子报表、自定义函数、脚本和事件处理等方面。此外，还可能包含一些示例代码和最佳实践，以帮助读者将理论知识应用于实际项目。《The JasperReports Ultimate Guide》是一本全面的教程，对于想要精通JasperReports的开发者和数据分析师而言，它提供了丰富的知识和实践经验，能够帮助他们有效地创建、管理和分发专业级别的业务报告。

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When compiling Java source files, the most important thing seems to be the classpath. If the Java

compiler does not find in the supplied classpath all the classes that are referenced by the source files it

tries to compile, the whole process fails and stops, the errors being displayed on the console.

The same happens also when JasperReports compiles the report expressions class. It is important then

to make sure we supply to the Java compiler at runtime the correct classpath for the compilation

process to succeed. For instance, we have to make sure that in the classpath we supply the custom

classes that we might use in the report expressions.

There is a default behavior for this aspect also. If no special classpath for compiling the report classes

is supplied, the engine will use the current JVM classpath returned by the system property

java.class.path. This default behavior can be overridden by putting the desired classpath in the

system property called

jasper.reports.compile.class.path.

You can see the jsp/compile.jsp and WEB-INF/classes/servlets/CompileServlet.java

files in the webapp sample provided, for the code snippet that makes use of this Java system properties

to override the default behavior of the JasperReports report compilation process.

Most of the time, compiling a report requires only a simple call to the JasperReports library like in the

following line of code:

dori.jasper.engine.JasperCompileManager.compileReport(myXmlFileName);

This call will produce the compiled report design and will store it in a file with the .jasper extension,

located in the same directory as the supplied XML report design file.

3.3 Report Design Preview

The JasperReports library is not shipped with an advanced GUI tool to help the design work. At this

time, there are at least 4 projects that try to provide such a tool.

However, the library contains a very helpful visual component that allows report creators to preview

the report designs as they build them.

The dori.jasper.view.JasperDesigner class is a simple Swing based Java application that can

load and display a report design either in its XML form or in the compiled form. Even if it is not a

complex GUI application, lacking advance functionality like the drag and dropping of the visual report

elements, it is very helpful instrument. All the supplied samples were created using this design viewer.

All the supplied samples have already prepared ANT tasks in their build.xml files that will launch

this design viewer for you to see the report designs.

In fact there are 2 ANT tasks for each sample report: viewDesign and viewDesignXML.

The first one loads the compiled report design that is normally found in the .jasper file. The second

one loads the XML report design, being the most useful since you can edit the XML file and push the

Reload button to immediately see the modification appearing on the screen.

If you have the ANT build tool installed on your system, in order to preview a sample report design,

you simply go to the desired sample directory and launch from the command line something like this:

>ant viewDesignXML

>ant viewDesign

In case you do not have ANT installed and you don't want to get it (you'll miss all the fun), here's the

complete command line that will launch the design viewer to preview one of the sample XML report

designs. We assume that you have a copy of the entire JasperReports source tree on your system

(Windows command line syntax):

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>java -classpath ./;../../../lib/commons-digester.jar;

../../../lib/commons-beanutils.jar;../../../lib/commons-collections.jar;

../../../lib/xerces.jar;../../../lib/jasperreports.jar

-Dorg.xml.sax.driver=org.apache.xerces.parsers.SAXParser

dori.jasper.view.JasperDesignViewer -XML -FFirstJasper.xml

By launching this command line, you should be able to see this window:

- figure 4 -

3.4 Filling Reports

The report filling process is the most important of all the JasperReports library functionality. It

represents the main objective for this piece of software, as it is the process that manipulates sets of data

in order to produce high quality documents, just like any reporting tool is supposed to do.

There are tree things that should be supplied to the report filling process as input:

· report design (report template);

· parameters;

· data source.

The output is always a single, final document that is ready to be viewed, printed or exported to other

rmats.

We have already seen that in order to fill a report, we are going to use the

dori.jasper.engine.JasperFillManager class. This class has various methods that allow us to

fill report designs that are located on disk, come from input streams or are supplied directly as in-

memory

dori.jasper.engine.JasperReport objects.

The output produced always corresponds to the type of the input received. That is, when receiving a

ile name for the report design, the generated report will be also placed in a file on disk. When the

report design is read from an input stream, the generated report will be written to an output stream and

so forth.

It might be that those various utility methods for filling the reports are not sufficient for a particular

application, who for example would want to load report designs as resources from classpath

and output

the generated documents to files on disk, at a certain location.

In such cases, the developers should consider

loading the report design objects before passing them to

the report filling routines, using the

dori.jasper.engine.util.JRLoader utility class. This way,

they could retrieve some report design properties such as the report name, so they can construct the

name of the resulting document, to place at the desired disk location.

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There are a lot of report filling scenarios that could be imagined in a real world application, and the

report filling manager class only tries to cover a portion of them, considered to be used more often. But

it should be no problem for anybody who might want to customize the report-filling process using the

library's basic functionality, as suggested above.

The report parameter values are supplied always packed in a

java.util.Map object, which has the

parameter names as its keys.

As for the third thing that the report filling process e

xpects to receive, the data source, there are two

different scenarios.

Normally, the engine works with an instance of the

dori.jasper.engine.JRDataSource interface,

from which it extracts the data when filling the report.

And the façade class

dori.jasper.engine.JasperFillManager has a full set of methods that

receive a

dori.jasper.engine.JRDataSource object as the data source of the report that is going

to be filled.

But there is another set of report filling methods in this manager class that receive a

java.sql.Connection object as a parameters, instead of expected data source object.

This is because most of the time reports are generated using data that comes from tables found in

relatio

nal databases.

Users have the possibility to specify the SQL query needed to retrieve the report data from the

dat

abase, in the report design itself. At runtime, the only thing the engine would need would be a JDBC

connection object to use in order to connect to the desired relational database, execute the SQL query

and retrieve the report data.

Behind the scenes, the engine will still use a special

dori.jasper.engine.JRDataSource object,

but this is preformed transparently for the calling program.

There are at least 4 sample applications provided with the project, which fill the reports using data from

also supplied HSQL database server. Those are jasper, query, scriptlet and subreport samples. To

run them, you have to start the HSQL database server first, by going to the

/demo/hsqldb directory of

the JasperReports project and launching this command:

>ant

>ant runServer

Note that you have to have ANT build tool installed on your system for you to launch the server in such

as simple manner. Otherwise you could still launch it like this:

>java -classpath ./;../../lib/hsqldb.jar org.hsqldb.Server

Here's a simple code snippet taken from the query sample that shows how to fill a report:

//Preparing parameters

Map parameters = new HashMap();

parameters.put("ReportTitle", "Address Report");

parameters.put("FilterClause", "'Boston', 'Chicago', 'Oslo'");

parameters.put("OrderClause", "City");

//Invoking the filling process

JasperFillManager.fillReportToFile(fileName, parameters, getConnection());

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