英文:
jsp - how to substitute deprecated ExpressionEvaluator
问题
我正在将一个应用程序迁移到JBoss EAP 7.4，该应用程序仍然使用JSP。大多数页面运行正常，但有一个页面让我头疼。该页面使用一个自定义TLD定义，该定义链接到一个类，该类扩展了javax.servlet.jsp.tagext.TagSupport；在doEndTag()方法中的这一点上，该类抛出了一个IllegalArgumentException，因为它无法将String转换为Detail：
ExpressionEvaluator eval = pageContext.getExpressionEvaluator();
Object ob = eval.evaluate(detail, Detail.class, pageContext.getVariableResolver(), new FunctionMapper(){public Method resolveFunction(String arg0, String arg1){return null;}}); //在这里崩溃
dettaglio = (Detail)ob; //无法达到这里
在我的依赖项中，我有javax.servlet-api版本3.0.1（scope=provided），并让JBoss处理其余的依赖项。
现在这个ExpressionEvaluator已经被弃用：
已弃用。从JSP 2.1开始，已被ExpressionFactory替代
ExpressionFactory是抽象的，不提供“eval”方法，所以我不知道如何替换它。应该如何替换它？如何修复这个错误？
谢谢。
英文:
I am porting an application to JBoss EAP 7.4 that still uses JSP. Most of the pages work fine but a page is giving me trouble. The page uses a custom TLD definition which is linked to a class, which extends javax.servlet.jsp.tagext.TagSupport; this class throws an IllegalArgumentException at this point in the doEndTag() method because it can't convert String to Detail:
ExpressionEvaluator eval = pageContext.getExpressionEvaluator();
Object ob = eval.evaluate(detail, Detail.class, pageContext.getVariableResolver(), new FunctionMapper(){public Method resolveFunction(String arg0, String arg1){return null;}}); //Crashes here
dettaglio = (Detail)ob; //does not reach this
In my dependencies I have javax.servlet-api version 3.0.1 (scope=provided) and I let JBoss handle the rest of the dependencies.
Now this ExpressionEvaluator has been deprecated:
Deprecated. As of JSP 2.1, replaced by ExpressionFactory
ExpressionFactory is abstract and does NOT provide an "eval" method, so I don't know how to replace it. How should it be replaced? How can I fix this error?
Thank you.
答案1
得分: 0
我认为我找到了一个解决办法：
ExpressionFactory factory = JspFactory.getDefaultFactory().getJspApplicationContext(pageContext.getServletContext()).getExpressionFactory();
ValueExpression valueExp = factory.createValueExpression(pageContext.getELContext(), ""${"+getDetail()+"}"", Detail.class);
dettaglio = (Detail) valueExp.getValue(pageContext.getELContext());
其中 "detail" 是我 JSP 页面中的属性。唯一的区别是，我只需在 JSP 中编写要解析的变量名称，而不是使用 ${} 符号。
英文:
I think I found a way around it:
ExpressionFactory factory = JspFactory.getDefaultFactory().getJspApplicationContext(pageContext.getServletContext()).getExpressionFactory();
ValueExpression valueExp = factory.createValueExpression(pageContext.getELContext(), "${"+getDetail()+"}", Detail.class);
dettaglio = (Detail) valueExp.getValue(pageContext.getELContext());
where "detail" is the attribute in my JSP Page. The only difference is that I had to simply write the name of the variable to parse in the JSP instead of using the ${} notation.
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