我正在使用DynamicReports 4.1.1。因为我依赖Java 1.6。问题是,无论使用哪种导出格式,我的所有报告都是空的。 pdf大约有1600字节,因此编写此类文件没有问题。但没有内容。我已经读到,如果数据源为空,则可能会发生这种情况,但是这里不是这种情况。有人有主意吗?
private void build() {
try {
JRDataSource c = new JRBeanCollectionDataSource(createDataSource());
report()
.setTemplate(Templates.reportTemplate)
.columns(
col.column("Item", "item", type.stringType()),
col.column("Quantity", "quantity", type.integerType()),
col.column("Unit price", "unitPrice", type.bigDecimalType()))
.title(Templates.createTitleComponent("CollectionDatasource"))
.detailFooter(cmp.line())
.pageFooter(Templates.footerComponent)
.noData(Templates.createTitleComponent("NoData"), cmp.text("There is no data"))
.setDataSource(c);
report().toPdf(new FileOutputStream("report4.pdf"));
} catch (DRException e) {
e.printStackTrace();
}
}
private List<Data> createDataSource() {
List<Data> data = new ArrayList<Data>();
data.add(new Data("DVD", 5, new BigDecimal(30)));
data.add(new Data("Book", 8, new BigDecimal(11)));
data.add(new Data("PDA", 2, new BigDecimal(15)));
return data;
}
private class Data {
private String item;
private Integer quantity;
private BigDecimal unitPrice;
public Data(String item, Integer quantity, BigDecimal unitPrice) {
this.item = item;
this.quantity = quantity;
this.unitPrice = unitPrice;
}
public String getItem() {
return item;
}
public void setItem(String item) {
this.item = item;
}
public Integer getQuantity() {
return quantity;
}
public void setQuantity(Integer quantity) {
this.quantity = quantity;
}
public BigDecimal getUnitPrice() {
return unitPrice;
}
public void setUnitPrice(BigDecimal unitPrice) {
this.unitPrice = unitPrice;
}
@Override
public String toString() {
return "Data{" + "item=" + item + ", quantity=" + quantity + ", unitPrice=" + unitPrice + '}';
}
}
最佳答案
怎么了?
您犯了一个小错误(看起来像复制和粘贴问题)-您是从未正确初始化的JasperReportBuilder对象生成代码的。
您创建了JasperReportBuilder类的两个实例:
report()
.setTemplate(Templates.reportTemplate)
.columns(
col.column("Item", "item", type.stringType()),
col.column("Quantity", "quantity", type.integerType()),
col.column("Unit price", "unitPrice", type.bigDecimalType()))
.title(Templates.createTitleComponent("CollectionDatasource"))
.detailFooter(cmp.line())
.pageFooter(Templates.footerComponent)
.noData(Templates.createTitleComponent("NoData"), cmp.text("There is no data"))
.setDataSource(c); // here is a first instance. It is initialized via builde. You should use instance for any actions
report().toPdf(new FileOutputStream("report4.pdf")); // the second instance. Just "blank" object, you are missed initializing via builder
您的情况下的有效代码为:
report()
.setTemplate(Templates.reportTemplate)
.columns(
col.column("Item", "item", type.stringType()),
col.column("Quantity", "quantity", type.integerType()),
col.column("Unit price", "unitPrice", type.bigDecimalType()))
.title(Templates.createTitleComponent("CollectionDatasource"))
.detailFooter(cmp.line())
.pageFooter(Templates.footerComponent)
.noData(Templates.createTitleComponent("NoData"), cmp.text("There is no data"))
.setDataSource(c)
.toPdf(new FileOutputStream("report4.pdf")); // we are not breaking the chain
要么:
JasperReportBuilder report = report()
.setTemplate(Templates.reportTemplate)
.columns(
col.column("Item", "item", type.stringType()),
col.column("Quantity", "quantity", type.integerType()),
col.column("Unit price", "unitPrice", type.bigDecimalType()))
.title(Templates.createTitleComponent("CollectionDatasource"))
.detailFooter(cmp.line())
.pageFooter(Templates.footerComponent)
.noData(Templates.createTitleComponent("NoData"), cmp.text("There is no data"))
.setDataSource(c); // we are created design, set styles and datasource and so on for our builder
report.toPdf(new FileOutputStream("report4.pdf")); // we are using the valid builder prepared at previous step
细节
这只是一个构建器模式,在这里没有魔术。
让我们看一下DynamicReports.report()方法的源代码。
public class DynamicReports {
// some members
public DynamicReports() {
}
public static JasperReportBuilder report() {
return new JasperReportBuilder();
}
如您所见,每次调用
DynamicReports.report()
方法都会创建一个新对象。这里没有单例或静态成员。