我想像这样在 TextField 表达式中使用 lambda 表达式:

Arrays.asList($F{field1}, $F{field2}, $F{field3}).stream().filter(i -> i != null).collect(java.util.stream.Collectors.joining(" / "))

假设这些字段的值:

$F{field1} = 1
$F{field2} = null
$F{field3} = 2

TextField 评估的预期结果是:

1 / 2

而不是我在 IDE 中收到错误:

Lambda expressions are allowed only at source level 1.8 or above

这是编译过程中 IDE 内部的异常:

net.sf.jasperreports.engine.JRException: Errors were encountered when compiling report expressions class file:
1. Lambda expressions are allowed only at source level 1.8 or above
                value = "Contato: " + Arrays.asList(((java.lang.String)field_c_telefone.getValue()), ((java.lang.String)field_c_celular.getValue()), ((java.lang.String)field_c_fax.getValue()), ((java.lang.String)field_c_email.getValue())).stream().filter(i -> i != null).collect(java.util.stream.Collectors.joining(" / ")); //$JR_EXPR_ID=22$
                                                                                                                                                                                                                                                               <------------>
2. Lambda expressions are allowed only at source level 1.8 or above
                value = "Contato: " + Arrays.asList(((java.lang.String)field_c_telefone.getOldValue()), ((java.lang.String)field_c_celular.getOldValue()), ((java.lang.String)field_c_fax.getOldValue()), ((java.lang.String)field_c_email.getOldValue())).stream().filter(i -> i != null).collect(java.util.stream.Collectors.joining(" / ")); //$JR_EXPR_ID=22$
                                                                                                                                                                                                                                                                           <------------>
3. Lambda expressions are allowed only at source level 1.8 or above
                value = "Contato: " + Arrays.asList(((java.lang.String)field_c_telefone.getValue()), ((java.lang.String)field_c_celular.getValue()), ((java.lang.String)field_c_fax.getValue()), ((java.lang.String)field_c_email.getValue())).stream().filter(i -> i != null).collect(java.util.stream.Collectors.joining(" / ")); //$JR_EXPR_ID=22$
                                                                                                                                                                                                                                                               <------------>
3 errors
.

    at net.sf.jasperreports.engine.design.JRAbstractCompiler.compileReport(JRAbstractCompiler.java:206)

    at net.sf.jasperreports.eclipse.builder.JasperReportCompiler.compileReport(JasperReportCompiler.java:294)

    at net.sf.jasperreports.eclipse.builder.JasperReportCompiler.compileReport(JasperReportCompiler.java:146)

    at net.sf.jasperreports.eclipse.builder.JasperReportsBuilder.compileJRXML(JasperReportsBuilder.java:220)

    at com.jaspersoft.studio.editor.action.CompileAction.actionCompile(CompileAction.java:142)

    at com.jaspersoft.studio.editor.action.CompileAction$1.run(CompileAction.java:93)

    at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

我已经将报告项目更改为使用 JRE System 1.8，但错误仍然存​​在。

我该如何解决？ jasper 编译器是否支持 lambda？

最佳答案

要启用 Java 8 支持，请尝试将这 3 个参数添加到 Jaspersoft Studio.ini 文件(位于 \TIBCO\Jaspersoft Studio- 6.x.final文件夹):

-Dorg.eclipse.jdt.core.compiler.codegen.targetPlatform=1.8
-Dorg.eclipse.jdt.core.compiler.compliance=1.8
-Dorg.eclipse.jdt.core.compiler.source=1.8

我的 ini 文件如下所示(Jaspersoft Studio 6.3.1 版本):

-startup
plugins/org.eclipse.equinox.launcher_1.3.100.v20150511-1540.jar
--launcher.library
plugins/org.eclipse.equinox.launcher.win32.win32.x86_64_1.1.300.v20150602-1417
-data
@noDefault
--launcher.defaultAction
openFile
-vm
features/jre.win32.win32.x86_64.feature_1.8.0.u92/jre/bin
-vmargs
-Xms128m
-Xmx1024m
-XX:+CMSClassUnloadingEnabled
-XX:+UseConcMarkSweepGC
-Dfile.encoding=UTF-8
-Djava.net.preferIPv4Stack=true
-Dorg.eclipse.jdt.core.compiler.codegen.targetPlatform=1.8
-Dorg.eclipse.jdt.core.compiler.compliance=1.8
-Dorg.eclipse.jdt.core.compiler.source=1.8

我检查了这份报告，它编译并运行良好:

<?xml version="1.0" encoding="UTF-8"?>
<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="java8support" pageWidth="595" pageHeight="842" whenNoDataType="NoDataSection" columnWidth="555" leftMargin="20" rightMargin="20" topMargin="20" bottomMargin="20">
    <property name="com.jaspersoft.studio.data.defaultdataadapter" value="One Empty Record"/>
    <parameter name="p1" class="java.lang.String" isForPrompting="false">
            <defaultValueExpression><![CDATA["1"]]></defaultValueExpression>
    </parameter>
    <parameter name="p2" class="java.lang.String" isForPrompting="false">
            <defaultValueExpression><![CDATA["2"]]></defaultValueExpression>
    </parameter>
    <title>
        <band height="79" splitType="Stretch">
            <textField>
                <reportElement x="80" y="20" width="234" height="30"/>
                <textFieldExpression><![CDATA[Arrays.asList($P{p1}, $P{p2}).stream().filter(i -> i != null).collect(java.util.stream.Collectors.joining(" / "))]]></textFieldExpression>
            </textField>
        </band>
    </title>
</jasperReport>

编译结果:

在JSS中生成的结果:

备注

我在 JSS 中没有使用这 3 个参数时遇到了同样的错误(Lambda 表达式仅在源级别 1.8 或更高版本中被允许):

有关如何从 Java 项目编译模板的更多信息，请参见帖子:

• How to use lambda expression in jrxml file?
• What version of JaspeReports has support for Java 8?
• Does JDK 8 supports JasperReports 6?

关于java - 在 Jaspersoft Studio 6.3 中的 TextField 表达式中使用 lambda 表达式，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/41618362/