JesperReport 与 Hibernate应用

如何使用Hibernate查询结果作为报表数据源，制作JasperReport报表。

 

1、如果Hibernate查询结果是一个简单对象集合，JasperReport类库中JRBeanCollectionDataSource类是一个不错的选择：

代码片段：

List cats = session.find("from eg.Cat"); Map parameters = new HashMap(); parameters.put("Title", "The Cat Report"); InputStream reportStream = this.class.getResourceAsStream("/the-cat-report.xml"); JasperDesign jasperDesign = JasperManager.loadXmlDesign(reportStream); JasperReport jasperReport = JasperManager.compileReport(jasperDesign); JRBeanCollectionDataSource ds = new JRBeanCollectionDataSource(cats); JasperPrint jasperPrint = JasperManager.fillReport(jasperReport, parameters, ds); JasperManager.printReportToPdfFile(jasperPrint, "the-cat-report.pdf");

以上代码解释见：JesperReport应用系列之入门篇4

2、如果Hibernate查询结果是数组（每个数组包含列表）下面这个例子是一个很好的解决方式

 

public class HibernateQueryResultDataSource implements JRDataSource { private String[] fields; private Iterator iterator; private Object currentValue; public HibernateQueryResultDataSource(List list, String[] fields) { this.fields = fields; this.iterator = list.iterator(); } public Object getFieldValue(JRField field) throws JRException { Object value = null; int index = getFieldIndex(field.getName()); if (index > -1) { Object[] values = (Object[])currentValue; value = values[index]; } return value; } public boolean next() throws JRException { currentValue = iterator.hasNext() ? iterator.next() : null; return (currentValue != null); } private int getFieldIndex(String field) { int index = -1; for (int i = 0; i < fields.length; i++) { if (fields[i].equals(field)) { index = i; break; } } return index; } }

 

我们可以用如下的方式引用：

 

List cats = session.find("select cat.type, cat.birthdate, cat.name from eg.DomesticCat cat"); Map parameters = new HashMap(); parameters.put("Title", "The Cat Report"); InputStream reportStream = this.class.getResourceAsStream("/the-cat-report.xml"); JasperDesign jasperDesign = JasperManager.loadXmlDesign(reportStream); JasperReport jasperReport = JasperManager.compileReport(jasperDesign); String[] fields = new String[] { "type", "birthdate", "name"}; HibernateQueryResultDataSource ds = new HibernateQueryResultDataSource(cats, fields); JasperPrint jasperPrint = JasperManager.fillReport(jasperReport, parameters, ds); JasperManager.printReportToPdfFile(jasperPrint, "the-cat-report.pdf");

 

另外一种HibernateQueryResultDataSource实现方式

public class HibernateQueryResultDataSource implements JRDataSource { private static final transient Logger logger = Logger.Factory.getInstance(HibernateQueryResultDataSource.class); protected HashMap fieldsToIdxMap=new HashMap(); protected Iterator iterator; protected Object currentValue; List values; public HibernateQueryResultDataSource(List list, String query) { int start =query.indexOf("select "); int stop =query.indexOf(" from "); Assertion.assertTrue( (start!=-1) && (stop!=-1), "The query "+ query+ " must be of the form select x,x from ..." ); start+="select".length(); String parameters=query.substring(start,stop); parameters=parameters.trim(); Assertion.assertTrue( parameters.length()>0, "The query "+ query+ " seems to be weird" ); StringTokenizer tokenizer=new StringTokenizer(parameters,","); int idx=0; while( tokenizer.hasMoreTokens() ) { String parameter=tokenizer.nextToken(); fieldsToIdxMap.put( parameter.trim(), new Integer(idx) ); idx++; } values=list; this.iterator = list.iterator(); } public Object getFieldValue(JRField field) throws JRException { String fieldName=field.getName().replace('_','.'); //JasperReports does not allow '.' in field names, so we //use '_' for nested properties instead and must convert here //(comment added by kbrown) Integer idxInt=(Integer) fieldsToIdxMap.get(fieldName); if (idxInt==null) { Assertion.fail( "The field /""+ fieldName+ "/" did not have an index mapping. Should be one off "+ fieldsToIdxMap.keySet() ); } Object[] values = (Object[]) currentValue; Assertion.assertTrue( idxInt.intValue()<values.length, "The index from field "+ fieldName+ " was illegal" ); Object value= values[ idxInt.intValue() ]; if ( logger.isDebugEnabled() ) { logger.debug("fetched value "+value+" from field "+fieldName); } return value; } public boolean next() throws JRException { currentValue = iterator.hasNext() ? iterator.next() : null; return currentValue != null; } public List getValues() { return values; } }