升级JasperReport库后无法下载pdf

Question

我目前正在将 JasperReports 库从版本 6.0.4 升级到 7.0.0。我的系统当前正在使用以下 JasperReports 库：

• jasperreports-fonts-6.0.4.jar
• jasperreports-javaflow-6.0.4.jar

升级这些库及其依赖项和其他 JasperReports 库后：

• jasperreports-7.0.0.jar
• jasperreports-jdt-7.0.0.jar

尝试下载报告 (PDF) 时系统抛出错误。我的系统使用 Java Servlet。

系统错误：

ERROR http-nio-8080-exec-3 OCSASTDFP :: [O00045.java:281] :: net.sf.jasperreports.engine.JRException: Unable to load report
    at net.sf.jasperreports.engine.xml.JRXmlLoader.loadXML(JRXmlLoader.java:172)
    at net.sf.jasperreports.engine.xml.JRXmlLoader.load(JRXmlLoader.java:149)
    at net.sf.jasperreports.engine.xml.JRXmlLoader.load(JRXmlLoader.java:136)
    ...

Tomcat 错误：

org.apache.struts2.dispatcher.DefaultDispatcherErrorHandler - Exception occurred during processing request: Cannot invoke "java.io.PrintWriter.print(String)" because "this.pw" is null
java.lang.NullPointerException: Cannot invoke "java.io.PrintWriter.print(String)" because "this.pw" is null
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
    at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
    at ognl.OgnlRuntime.invokeMethodInsideSandbox(OgnlRuntime.java:1245) ~[ognl-3.3.3.jar:?]
    at ognl.OgnlRuntime.invokeMethod(OgnlRuntime.java:1230) ~[ognl-3.3.3.jar:?]
    at ognl.OgnlRuntime.callAppropriateMethod(OgnlRuntime.java:1958) ~[ognl-3.3.3.jar:?]
    at ognl.ObjectMethodAccessor.callMethod(ObjectMethodAccessor.java:68) ~[ognl-3.3.3.jar:?]
    at com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethodWithDebugInfo(XWorkMethodAccessor.java:98) ~[struts2-core-6.0.3.jar:6.0.3]
    at com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethod(XWorkMethodAccessor.java:90) ~[struts2-core-6.0.3.jar:6.0.3]

我尝试遵循 StackOverflow 和 Jasper 社区的一些建议，包括添加：

• jasperreports-7.0.0.jar
• jasperreports-jdt-7.0.0.jar

但是，这个问题仍然存在。

Answer 1

我在升级到 JasperReports 7.0.1时遇到了同样的问题。我通过将

jasperreports-excel-poi

依赖项添加到我的项目中解决了这个问题。

    <dependency>
        <groupId>net.sf.jasperreports</groupId>
        <artifactId>jasperreports-excel-poi</artifactId>
        <version>7.0.1</version>
    </dependency>