尝试从查询中显示值后的java.lang.NumberFormatException

Question

public List findCatalog() {
    Query query = getEntityManager().createQuery("SELECT pc.productCatalog, p.name, p.product FROM ProductCatalog pc JOIN pc.products p");
    return query.getResultList();
}

您好,有了这样的查询我的应用程序编译好了.但是,当我打开执行此查询的页面时,我收到以下错误:

org.apache.jasper.JasperException:java.lang.NumberFormatException:对于输入字符串:"productCatalog"

productCatalog是我的主键,但是当我只包含name列时也会发生同样的情况

异常org.apache.jasper.JasperException:java.lang.NumberFormatException:对于输入字符串:"name"根本原因

java.lang.NumberFormatException:对于输入字符串:"name"

如果我没有在我的查询中进行连接,则可以打印1个表中的结果.我现在无能为力,问题可能是,我已经阅读了Pro JPA 2书,官方java EE 6教程,googled很多.表设计是ManyToMany.我有产品表,*product_catalog*表和绑定表*product_product_catalog.我在绑定表中没有外键.我使用NetBeans EclipseLink向导创建了实体和外观类.

这是我如何在我的ProductCatalog类上映射多对多的关系

@ManyToMany
    @JoinTable(name = "product_product_catalog",
    joinColumns = {
        @JoinColumn(name = "product_catalog")
    },
    inverseJoinColumns = {
        @JoinColumn(name = "product")
    })
    private Collection<Product> products;

product和product_catalog是相应表的主键.现在我不知道我哪里错了,也许是映射错了？虽然我见过的很多例子都有相同的映射实现,但是在他们的表中他们有外键,这可能是个问题吗？正如我所说,如果我不加入第二张桌子,一切都运作良好.

这是我的servlet初始化该方法 getServletContext().setAttribute("productCatalog", productCatalogFacade.findCatalog());

这是我的JSP页面片段

<table>
            <c:forEach var="list" items="${productCatalog}" varStatus="iter">
                <tr>
                    <td>${list.productCatalog}</td>
                    <td>${list.product}</td>
                    <td>${list.name}</td>
                </tr>
            </c:forEach>
        </table>

这是我的本机SQL查询,我正在努力实现

SELECT PPC.product_product_catalog, PPC.product_catalog, PPC.product, P.name, PC.name AS  "catalog name", P.code, P.description, P.price, P.producer
FROM product_catalog PC
INNER JOIN product_product_catalog PPC ON PC.product_catalog = PPC.product_catalog
INNER JOIN product P ON P.product = PPC.product

这里我的最后一段代码是当我去执行查询的页面时glassfish产生的输出:

WARNING: StandardWrapperValve[jsp]: PWC1406: Servlet.service() for servlet jsp threw exception
java.lang.NumberFormatException: For input string: "productCatalog"
        at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
        at java.lang.Integer.parseInt(Integer.java:449)
        at java.lang.Integer.parseInt(Integer.java:499)
        at javax.el.ArrayELResolver.toInteger(ArrayELResolver.java:375)
        at javax.el.ArrayELResolver.getValue(ArrayELResolver.java:195)
        at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:175)
        at com.sun.el.parser.AstValue.getValue(AstValue.java:116)
        at com.sun.el.parser.AstValue.getValue(AstValue.java:163)
        at com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:219)
        at org.apache.jasper.runtime.PageContextImpl.evaluateExpression(PageContextImpl.java:1007)
        at org.apache.jsp.index_jsp._jspx_meth_c_forEach_0(index_jsp.java from :206)
        at org.apache.jsp.index_jsp._jspService(index_jsp.java from :137)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:109)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:406)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:483)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:373)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
        at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1523)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:279)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:188)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:641)
        at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:97)
        at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:85)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:185)
        at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:325)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:226)
        at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:165)
        at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:791)
        at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:693)
        at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:954)
        at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:170)
        at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:135)
        at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:102)
        at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:88)
        at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:76)
        at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:53)
        at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:57)
        at com.sun.grizzly.ContextTask.run(ContextTask.java:69)
        at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:330)
        at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:309)
        at java.lang.Thread.run(Thread.java:619)

Answer 1

当您在SELECT子句中执行包含许多变量的请求时,例如

SELECT pc.productCatalog, p.name, p.product ...

每行结果都以形式返回Object[],因此您需要使用数字索引来访问其元素:

<c:forEach var="list" items="${productCatalog}" varStatus="iter"><tr>
    <td>${list[0]}</td> 
    <td>${list[2]}</td>
    <td>${list[1]}</td>
</tr></c:forEach>