Java tutorial
/******************************************************************************* * This file is part of OpenNMS(R). * * Copyright (C) 2010-2014 The OpenNMS Group, Inc. * OpenNMS(R) is Copyright (C) 1999-2014 The OpenNMS Group, Inc. * * OpenNMS(R) is a registered trademark of The OpenNMS Group, Inc. * * OpenNMS(R) is free software: you can redistribute it and/or modify * it under the terms of the GNU Affero General Public License as published * by the Free Software Foundation, either version 3 of the License, * or (at your option) any later version. * * OpenNMS(R) is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Affero General Public License for more details. * * You should have received a copy of the GNU Affero General Public License * along with OpenNMS(R). If not, see: * http://www.gnu.org/licenses/ * * For more information contact: * OpenNMS(R) Licensing <license@opennms.org> * http://www.opennms.org/ * http://www.opennms.com/ *******************************************************************************/ package org.opennms.reporting.jasperreports.svclayer; import java.io.File; import java.io.OutputStream; import java.sql.Connection; import java.text.SimpleDateFormat; import java.util.ArrayList; import java.util.Calendar; import java.util.Date; import java.util.HashMap; import java.util.Iterator; import java.util.List; import java.util.Map; import java.util.Objects; import java.util.ServiceLoader; import java.util.concurrent.Callable; import org.apache.commons.jexl2.JexlEngine; import org.apache.commons.jexl2.MapContext; import org.opennms.api.reporting.ReportException; import org.opennms.api.reporting.ReportFormat; import org.opennms.api.reporting.ReportService; import org.opennms.api.reporting.parameter.ReportDateParm; import org.opennms.api.reporting.parameter.ReportDoubleParm; import org.opennms.api.reporting.parameter.ReportFloatParm; import org.opennms.api.reporting.parameter.ReportIntParm; import org.opennms.api.reporting.parameter.ReportParameters; import org.opennms.api.reporting.parameter.ReportStringParm; import org.opennms.core.db.DataSourceFactory; import org.opennms.core.logging.Logging; import org.opennms.core.utils.DBUtils; import org.opennms.features.reporting.repository.global.GlobalReportRepository; import org.opennms.reporting.jasperreports.compiler.CustomJRJdtCompiler; import org.opennms.reporting.jasperreports.filter.ParameterFilter; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import net.sf.jasperreports.engine.JREmptyDataSource; import net.sf.jasperreports.engine.JRException; import net.sf.jasperreports.engine.JRExporterParameter; import net.sf.jasperreports.engine.JRExpression; import net.sf.jasperreports.engine.JRParameter; import net.sf.jasperreports.engine.JRPropertiesUtil; import net.sf.jasperreports.engine.JRReport; import net.sf.jasperreports.engine.JRSubreport; import net.sf.jasperreports.engine.JasperCompileManager; import net.sf.jasperreports.engine.JasperExportManager; import net.sf.jasperreports.engine.JasperFillManager; import net.sf.jasperreports.engine.JasperPrint; import net.sf.jasperreports.engine.JasperReport; import net.sf.jasperreports.engine.JasperReportsContext; import net.sf.jasperreports.engine.SimpleJasperReportsContext; import net.sf.jasperreports.engine.design.JRCompiler; import net.sf.jasperreports.engine.design.JasperDesign; import net.sf.jasperreports.engine.export.JRCsvExporter; import net.sf.jasperreports.engine.fill.JRParameterDefaultValuesEvaluator; import net.sf.jasperreports.engine.util.JRElementsVisitor; import net.sf.jasperreports.engine.util.JRLoader; import net.sf.jasperreports.engine.util.JRSaver; import net.sf.jasperreports.engine.util.JRVisitorSupport; import net.sf.jasperreports.engine.xml.JRPrintXmlLoader; import net.sf.jasperreports.engine.xml.JRXmlLoader; /** * <p> * JasperReportService class. * </p> * * @author jonathan@opennms.org * @version $Id: $ */ public class JasperReportService implements ReportService { private static final Logger LOG = LoggerFactory.getLogger(JasperReportService.class); private static final String LOG4J_CATEGORY = "reports"; private static final String STRING_INPUT_TYPE = "org.opennms.report.stringInputType"; private GlobalReportRepository m_globalReportRepository; private final List<ParameterFilter> parameterFilters; public JasperReportService() { parameterFilters = new ArrayList<>(); Iterator<ParameterFilter> it = ServiceLoader.load(ParameterFilter.class).iterator(); while (it.hasNext()) { parameterFilters.add(it.next()); } } /** * {@inheritDoc} */ @Override public List<ReportFormat> getFormats(String reportId) { List<ReportFormat> formats = new ArrayList<ReportFormat>(); formats.add(ReportFormat.PDF); formats.add(ReportFormat.CSV); return formats; } /** * {@inheritDoc} * * @throws ReportException */ @Override public ReportParameters getParameters(final String reportId) throws ReportException { try { return Logging.withPrefix(LOG4J_CATEGORY, new Callable<ReportParameters>() { @Override public ReportParameters call() throws Exception { final ReportParameters reportParameters = new ReportParameters(); final JasperReport jasperReport = getJasperReport(reportId); final Map<String, Object> defaultValues = JRParameterDefaultValuesEvaluator .evaluateParameterDefaultValues(jasperReport, new HashMap<>()); final JRParameter[] reportParms = jasperReport.getParameters(); final List<ReportIntParm> intParms = new ArrayList<ReportIntParm>(); reportParameters.setIntParms(intParms); final List<ReportFloatParm> floatParms = new ArrayList<ReportFloatParm>(); reportParameters.setFloatParms(floatParms); final List<ReportDoubleParm> doubleParms = new ArrayList<ReportDoubleParm>(); reportParameters.setDoubleParms(doubleParms); final List<ReportStringParm> stringParms = new ArrayList<ReportStringParm>(); reportParameters.setStringParms(stringParms); final List<ReportDateParm> dateParms = new ArrayList<ReportDateParm>(); reportParameters.setDateParms(dateParms); for (final JRParameter reportParm : reportParms) { if (apply(parameterFilters, reportParm)) { if (reportParm.getValueClassName().equals("java.lang.String")) { LOG.debug("adding a string parm name {}", reportParm.getName()); final ReportStringParm stringParm = new ReportStringParm(); if (reportParm.getDescription() != null) { stringParm.setDisplayName(reportParm.getDescription()); } else { stringParm.setDisplayName(reportParm.getName()); } if (reportParm.getPropertiesMap().containsProperty(STRING_INPUT_TYPE)) { stringParm.setInputType( reportParm.getPropertiesMap().getProperty(STRING_INPUT_TYPE)); } stringParm.setName(reportParm.getName()); if (defaultValues.containsKey(reportParm.getName()) && (defaultValues.get(reportParm.getName()) != null)) { stringParm.setValue((String) defaultValues.get(reportParm.getName())); } else { stringParm.setValue(""); } stringParms.add(stringParm); continue; } if (reportParm.getValueClassName().equals("java.lang.Integer")) { LOG.debug("adding a Integer parm name {}", reportParm.getName()); final ReportIntParm intParm = new ReportIntParm(); if (reportParm.getDescription() != null) { intParm.setDisplayName(reportParm.getDescription()); } else { intParm.setDisplayName(reportParm.getName()); } intParm.setName(reportParm.getName()); if (defaultValues.containsKey(reportParm.getName()) && (defaultValues.get(reportParm.getName()) != null)) { intParm.setValue((Integer) defaultValues.get(reportParm.getName())); } else { intParm.setValue(Integer.valueOf(0)); } intParms.add(intParm); continue; } if (reportParm.getValueClassName().equals("java.lang.Float")) { LOG.debug("adding a Float parm name {}", reportParm.getName()); final ReportFloatParm floatParm = new ReportFloatParm(); if (reportParm.getDescription() != null) { floatParm.setDisplayName(reportParm.getDescription()); } else { floatParm.setDisplayName(reportParm.getName()); } floatParm.setName(reportParm.getName()); if (defaultValues.containsKey(reportParm.getName()) && (defaultValues.get(reportParm.getName()) != null)) { floatParm.setValue((Float) defaultValues.get(reportParm.getName())); } else { floatParm.setValue(new Float(0)); } floatParms.add(floatParm); continue; } if (reportParm.getValueClassName().equals("java.lang.Double")) { LOG.debug("adding a Double parm name {}", reportParm.getName()); final ReportDoubleParm doubleParm = new ReportDoubleParm(); if (reportParm.getDescription() != null) { doubleParm.setDisplayName(reportParm.getDescription()); } else { doubleParm.setDisplayName(reportParm.getName()); } doubleParm.setName(reportParm.getName()); if (defaultValues.containsKey(reportParm.getName()) && (defaultValues.get(reportParm.getName()) != null)) { doubleParm.setValue((Double) defaultValues.get(reportParm.getName())); } else { doubleParm.setValue(Double.valueOf(0)); } doubleParms.add(doubleParm); continue; } if (reportParm.getValueClassName().equals("java.util.Date")) { LOG.debug("adding a java.util.Date parm name {}", reportParm.getName()); final ReportDateParm dateParm = new ReportDateParm(); dateParm.setUseAbsoluteDate(false); if (reportParm.getDescription() != null) { dateParm.setDisplayName(reportParm.getDescription()); } else { dateParm.setDisplayName(reportParm.getName()); } dateParm.setName(reportParm.getName()); dateParm.setCount(Integer.valueOf(1)); dateParm.setInterval("day"); dateParm.setHours(0); dateParm.setMinutes(0); if (defaultValues.containsKey(reportParm.getName()) && (defaultValues.get(reportParm.getName()) != null)) { dateParm.setDate((Date) defaultValues.get(reportParm.getName())); Calendar cal = Calendar.getInstance(); cal.setTime(dateParm.getDate()); dateParm.setMinutes(cal.get(Calendar.MINUTE)); dateParm.setHours(cal.get(Calendar.HOUR_OF_DAY)); } else { final Calendar cal = Calendar.getInstance(); cal.set(Calendar.HOUR_OF_DAY, 0); cal.set(Calendar.MINUTE, 0); cal.set(Calendar.SECOND, 0); cal.set(Calendar.MILLISECOND, 0); dateParm.setDate(cal.getTime()); } dateParms.add(dateParm); continue; } if (reportParm.getValueClassName().equals("java.sql.Date") || reportParm.getValueClassName().equals("java.sql.Timestamp")) { LOG.debug("adding a java.sql.Date or Timestamp parm name {}", reportParm.getName()); final ReportDateParm dateParm = new ReportDateParm(); dateParm.setUseAbsoluteDate(false); if (reportParm.getDescription() != null) { dateParm.setDisplayName(reportParm.getDescription()); } else { dateParm.setDisplayName(reportParm.getName()); } dateParm.setName(reportParm.getName()); dateParm.setCount(Integer.valueOf(1)); dateParm.setInterval("day"); dateParm.setHours(0); dateParm.setMinutes(0); if (defaultValues.containsKey(reportParm.getName()) && (defaultValues.get(reportParm.getName()) != null)) { dateParm.setDate((Date) defaultValues.get(reportParm.getName())); Calendar cal = Calendar.getInstance(); cal.setTime(dateParm.getDate()); dateParm.setMinutes(cal.get(Calendar.MINUTE)); dateParm.setHours(cal.get(Calendar.HOUR_OF_DAY)); } else { final Calendar cal = Calendar.getInstance(); cal.set(Calendar.HOUR_OF_DAY, 0); cal.set(Calendar.MINUTE, 0); cal.set(Calendar.SECOND, 0); cal.set(Calendar.MILLISECOND, 0); dateParm.setDate(cal.getTime()); } dateParms.add(dateParm); continue; } throw new ReportException( "Unsupported report parameter type " + reportParm.getValueClassName()); } else { LOG.debug("SKIPPING {}", reportParm.getName()); } } return reportParameters; } }); } catch (final Exception e) { if (e instanceof ReportException) throw (ReportException) e; throw new ReportException(e); } } /** * {@inheritDoc} */ @Override public void render(final String reportId, final String location, final ReportFormat format, final OutputStream outputStream) throws ReportException { try { Logging.withPrefix(LOG4J_CATEGORY, new Callable<Void>() { @Override public Void call() throws Exception { try { final JasperPrint jasperPrint = getJasperPrint(location); switch (format) { case PDF: LOG.debug("rendering as PDF"); exportReportToPdf(jasperPrint, outputStream); break; case CSV: LOG.debug("rendering as CSV"); exportReportToCsv(jasperPrint, outputStream); break; default: LOG.debug("rendering as PDF as no valid format found"); exportReportToPdf(jasperPrint, outputStream); } } catch (final Exception e) { LOG.error("Unable to render report {}", reportId, e); throw new ReportException("Unable to render report " + reportId, e); } return null; } }); } catch (final Exception e) { if (e instanceof ReportException) throw (ReportException) e; throw new ReportException(e); } } private JasperPrint getJasperPrint(String location) throws JRException { if (location.contains("jrpxml")) { return JRPrintXmlLoader.load(location); } else { return (JasperPrint) JRLoader.loadObject(new File(location)); } } /** * {@inheritDoc} */ @Override public String run(final Map<String, Object> reportParms, final String reportId) throws ReportException { try { return Logging.withPrefix(LOG4J_CATEGORY, new Callable<String>() { @Override public String call() throws Exception { final String baseDir = System.getProperty("opennms.report.dir"); final JasperReport jasperReport = getJasperReport(reportId); final Map<String, Object> jrReportParms = buildJRparameters(reportParms, jasperReport.getParameters()); // Find sub reports and provide sub reports as parameter jrReportParms.putAll(buildSubreport(reportId, jasperReport)); final String outputFileName = new String(baseDir + "/" + jasperReport.getName() + new SimpleDateFormat("-MMddyyyy-HHmm").format(new Date()) + ".jrprint"); LOG.debug("jrprint output file: {}", outputFileName); try { if ("jdbc".equalsIgnoreCase(m_globalReportRepository.getEngine(reportId))) { final DBUtils db = new DBUtils(); try { final Connection connection = DataSourceFactory.getInstance().getConnection(); db.watch(connection); JasperFillManager.fillReportToFile(jasperReport, outputFileName, reportParms, connection); } finally { db.cleanUp(); } } else if (m_globalReportRepository.getEngine(reportId).equals("null")) { JasperFillManager.fillReportToFile(jasperReport, outputFileName, reportParms, new JREmptyDataSource()); } else { throw new ReportException("No suitable datasource configured for report " + reportId); } } catch (final Exception e) { LOG.warn("Failed to run report " + reportId, e); if (e instanceof ReportException) throw (ReportException) e; throw new ReportException(e); } return outputFileName; } }); } catch (final Exception e) { if (e instanceof ReportException) throw (ReportException) e; throw new ReportException("Failed to run Jasper report " + reportId, e); } } /** * Method to find all sub reports as parameter. Compile sub reports and put all compile sub reports in a parameter map. * Returned map is compatible to common jasper report parameter map. * * @param mainReportId String for specific main report identified by a report id * @param mainReport JasperReport a compiled main report * @return a sub report parameter map as {@link java.util.HashMap<String,Object>} object */ private Map<String, Object> buildSubreport(final String mainReportId, final JasperReport mainReport) throws ReportException { int idx = mainReportId.indexOf('_'); String repositoryId = idx > -1 ? mainReportId.substring(0, idx) : "local"; Map<String, Object> subreportMap = new HashMap<String, Object>(); // Filter parameter for sub reports for (JRParameter parameter : mainReport.getParameters()) { // We need only parameter for Sub reports and we *DON'T* need the default parameter JASPER_REPORT if ("net.sf.jasperreports.engine.JasperReport".equals(parameter.getValueClassName()) && !"JASPER_REPORT".equals(parameter.getName())) { subreportMap.put(parameter.getName(), parameter.getValueClassName()); } } for (final Map.Entry<String, Object> entry : subreportMap.entrySet()) { final String reportId = repositoryId + "_" + entry.getKey(); entry.setValue(getJasperReport(reportId)); } for (final Map.Entry<String, Object> entry : subreportMap.entrySet()) { LOG.debug("Key: {} - Value: {}", entry.getKey(), entry.getValue()); } return subreportMap; } /** * {@inheritDoc} */ @Override public void runAndRender(final Map<String, Object> reportParms, final String reportId, final ReportFormat format, final OutputStream outputStream) throws ReportException { try { Logging.withPrefix(LOG4J_CATEGORY, new Callable<Void>() { @Override public Void call() throws Exception { final JasperReport jasperReport = getJasperReport(reportId); final Map<String, Object> jrReportParms = buildJRparameters(reportParms, jasperReport.getParameters()); jrReportParms.putAll(buildSubreport(reportId, jasperReport)); if ("jdbc".equalsIgnoreCase(m_globalReportRepository.getEngine(reportId))) { final DBUtils db = new DBUtils(); try { final Connection connection = DataSourceFactory.getInstance().getConnection(); db.watch(connection); final JasperPrint jasperPrint = JasperFillManager.fillReport(jasperReport, jrReportParms, connection); exportReport(format, jasperPrint, outputStream); } finally { db.cleanUp(); } } else if ("null".equalsIgnoreCase(m_globalReportRepository.getEngine(reportId))) { final JasperPrint jasperPrint = JasperFillManager.fillReport(jasperReport, jrReportParms, new JREmptyDataSource()); exportReport(format, jasperPrint, outputStream); } return null; } }); } catch (final Exception e) { if (e instanceof ReportException) throw (ReportException) e; throw new ReportException("Failed to run Jasper report " + reportId, e); } } private void exportReport(ReportFormat format, JasperPrint jasperPrint, OutputStream outputStream) throws JRException { switch (format) { case PDF: exportReportToPdf(jasperPrint, outputStream); break; case CSV: exportReportToCsv(jasperPrint, outputStream); break; default: break; } } private void exportReportToPdf(final JasperPrint jasperPrint, final OutputStream outputStream) throws JRException { JasperExportManager.exportReportToPdfStream(jasperPrint, outputStream); } private void exportReportToCsv(final JasperPrint jasperPrint, final OutputStream outputStream) throws JRException { JRCsvExporter exporter = new JRCsvExporter(); exporter.setParameter(JRExporterParameter.JASPER_PRINT, jasperPrint); exporter.setParameter(JRExporterParameter.OUTPUT_STREAM, outputStream); exporter.exportReport(); } private Map<String, Object> buildJRparameters(final Map<String, Object> onmsReportParms, final JRParameter[] reportParms) throws ReportException { final Map<String, Object> jrReportParms = new HashMap<String, Object>(); for (final JRParameter reportParm : reportParms) { if (apply(getParameterFilters(), reportParm)) { final String parmName = reportParm.getName(); if (!onmsReportParms.containsKey(parmName)) { throw new ReportException( "Required parameter " + parmName + " not supplied to JasperReports by OpenNMS"); } if (reportParm.getValueClassName().equals("java.lang.String")) { jrReportParms.put(parmName, (String) onmsReportParms.get(parmName)); continue; } if (reportParm.getValueClassName().equals("java.lang.Integer")) { jrReportParms.put(parmName, (Integer) onmsReportParms.get(parmName)); continue; } if (reportParm.getValueClassName().equals("java.lang.Float")) { jrReportParms.put(parmName, (Float) onmsReportParms.get(parmName)); continue; } if (reportParm.getValueClassName().equals("java.lang.Double")) { jrReportParms.put(parmName, (Double) onmsReportParms.get(parmName)); continue; } if (reportParm.getValueClassName().equals("java.util.Date")) { jrReportParms.put(parmName, (Date) onmsReportParms.get(parmName)); continue; } if (reportParm.getValueClassName().equals("java.sql.Date")) { final Date date = (Date) onmsReportParms.get(parmName); jrReportParms.put(parmName, new java.sql.Date(date.getTime())); continue; } if (reportParm.getValueClassName().equals("java.sql.Timestamp")) { final Date date = (Date) onmsReportParms.get(parmName); jrReportParms.put(parmName, new java.sql.Timestamp(date.getTime())); continue; } throw new ReportException("Unsupported report parameter type " + reportParm.getValueClassName()); } } return jrReportParms; } /** * {@inheritDoc} */ @Override public boolean validate(final Map<String, Object> reportParms, final String reportId) { // returns true until we can take parameters return true; } public void setGlobalReportRepository(final GlobalReportRepository globalReportRepository) { m_globalReportRepository = globalReportRepository; } private JasperDesign getJasperDesign(String reportId) throws ReportException { try { JasperDesign jasperDesign = JRXmlLoader.load(m_globalReportRepository.getTemplateStream(reportId)); return jasperDesign; } catch (JRException e) { LOG.error("Unable to load report with id '{}'", reportId, e); throw new ReportException("Unable to load report with id '" + reportId + "'", e); } } private JasperReport getJasperReport(String reportId) throws ReportException { JasperDesign jasperDesign = getJasperDesign(reportId); return compileReport(jasperDesign); } /** * Compiles the given {@link JasperDesign} (*.jrxml) to a {@link JasperReport} (*.jasper) * * @param jasperDesign The Design (*.jrxml) to compile * @return The compiled report (*.jasper) * @throws ReportException If the design could not be compiled. */ private JasperReport compileReport(JasperDesign jasperDesign) throws ReportException { try { JasperReport report; // If the target report is written in Java, use our custom JDT compiler if (JRReport.LANGUAGE_JAVA.equals(jasperDesign.getLanguage())) { JasperReportsContext reportsContext = new SimpleJasperReportsContext(); JRPropertiesUtil.getInstance(reportsContext).setProperty( JRCompiler.COMPILER_PREFIX + JRReport.LANGUAGE_JAVA, CustomJRJdtCompiler.class.getCanonicalName()); JasperCompileManager jasperCompilerManager = JasperCompileManager.getInstance(reportsContext); report = jasperCompilerManager.compile(jasperDesign); } else { // Otherwise, use the default that Jasper providers report = JasperCompileManager.compileReport(jasperDesign); } for (Object eachKey : System.getProperties().keySet()) { String eachStringKey = (String) eachKey; if (eachStringKey.startsWith("net.sf.jasperreports")) { report.setProperty(eachStringKey, System.getProperty(eachStringKey)); } } compileSubreportsRecursively(report); return report; } catch (final JRException e) { LOG.error("unable to compile jasper report {}", e); throw new ReportException("unable to compile jasperReport", e); } } /** * Iterates recursively over each subreport element in the given {@link JasperReport} and compiles the referenced * subreport if not already compiled. * * @param report The {@link JasperReport} to compile all subreports recursively if needed. */ private void compileSubreportsRecursively(JasperReport report) { JRElementsVisitor.visitReport(report, new JRVisitorSupport() { @Override public void visitSubreport(JRSubreport subreport) { final String compiledSubreportName = evaluateToString(report, subreport.getExpression()); final String sourceSubreportName = compiledSubreportName.replace(".jasper", ".jrxml"); final File compiledSubreportFile = new File(compiledSubreportName); final File sourceSubreportFile = new File(sourceSubreportName); if (!compiledSubreportFile.exists() || compiledSubreportFile.lastModified() < sourceSubreportFile.lastModified()) { LOG.debug("Compiling Subreport '{}' ...", compiledSubreportName); try { JasperDesign subreportDesign = JRXmlLoader.load(sourceSubreportName); JasperReport subreportCompiled = compileReport(subreportDesign); JRSaver.saveObject(subreportCompiled, compiledSubreportFile); compileSubreportsRecursively(subreportCompiled); // Compile containing sub reports if needed } catch (ReportException | JRException e) { LOG.error("Could not compile Jasper Subreport. Expression: {}, Evaluated Expression: {}", subreport.getExpression(), compiledSubreportName, e); } LOG.debug("Subreport '{}' compiled", compiledSubreportName); } else { // The report is already compiled, compile containing sub reports if needed try { compileSubreportsRecursively((JasperReport) JRLoader.loadObject(compiledSubreportFile)); } catch (JRException e) { LOG.error( "Could not load compiled Jasper Subreport. Expression: {}, Evaluated Expression: {}", subreport.getExpression(), compiledSubreportName, e); } } } }); } protected boolean apply(List<ParameterFilter> parameterFilters, JRParameter reportParm) { LOG.debug("Found report parameter {} (isSystemDefined(){}, isForPrompting()={}", reportParm.getName(), reportParm.isSystemDefined(), reportParm.isForPrompting()); for (ParameterFilter eachFilter : parameterFilters) { if (!eachFilter.apply(reportParm)) { return false; } } return true; } protected List<ParameterFilter> getParameterFilters() { return parameterFilters; } public static String evaluateToString(JasperReport report, JRExpression expression) { Objects.requireNonNull(report); Objects.requireNonNull(expression); SubreportExpressionVisitor visitor = new SubreportExpressionVisitor(report); String string = visitor.visit(expression); if (string != null) { JexlEngine engine = new JexlEngine(); return (String) engine.createExpression(string).evaluate(new MapContext()); } return null; } }