以下是我的java代碼，是通過servlet請求的，list集合是通過資料庫查上來的，經測驗沒有問題。
package com.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Writer;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.entity.Food;
import com.entity.News;
import com.services.FoodService;
import com.services.NewsService;
import com.services.Impl.FoodServiceImpl;
import com.services.Impl.NewsServiceImpl;
import freemarker.template.*;
@WebServlet(urlPatterns={"/Index"} ,name="IndexServlet")
public class IndexServlet extends HttpServlet{
private Configuration cfg;
public void init() {
cfg = new Configuration();
cfg.setDefaultEncoding("UTF-8");
cfg.setServletContextForTemplateLoading(getServletContext(),
"WEB-INF/templates");
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
FoodService foodService = new FoodServiceImpl();
NewsService newsService = new NewsServiceImpl();
Map root = new HashMap();
List<Food> list = foodService.getFoodList();
root.put("foods", list);
// Map<String, Object> root1 = new HashMap<String, Object>();
// List<News> list1 = newsService.getNewsList();
// root1.put("list1", list1);
Template t = cfg.getTemplate("index.ftl");
response.setContentType("text/html; charset=" + t.getEncoding());
Writer out = response.getWriter();
try {
t.process(root, out, ObjectWrapper.BEANS_WRAPPER);
} catch (TemplateException e) {
throw new ServletException("處理模板有誤", e);
}finally{
if(out!=null){
out.close();
}
out.flush();
}
}
}
模板代碼
<html>
<body>
<#list foods as food>
${food.id}
${food.chineseName}
</#list>
</body>
</html>
報錯資訊
FreeMarker template error:
The following has evaluated to null or missing:
==> foods [in template "index.ftl" at line 3, column 16]
----
Tip: If the failing expression is known to be legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----
----
FTL stack trace ("~" means nesting-related):
- Failed at: #list foods as food [in template "index.ftl" at line 3, column 9]
----
Java stack trace (for programmers):
----
freemarker.core.InvalidReferenceException: [... Exception message was already printed; see it above ...]
at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:131)
at freemarker.core.Expression.assertNonNull(Expression.java:194)
at freemarker.core.IteratorBlock.acceptWithResult(IteratorBlock.java:74)
at freemarker.core.IteratorBlock.accept(IteratorBlock.java:64)
at freemarker.core.Environment.visit(Environment.java:324)
at freemarker.core.MixedContent.accept(MixedContent.java:54)
at freemarker.core.Environment.visit(Environment.java:324)
at freemarker.core.Environment.process(Environment.java:302)
at freemarker.template.Template.process(Template.java:325)
at com.servlet.IndexServlet.service(IndexServlet.java:67)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:506)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:962)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:452)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1087)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2536)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2525)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
uj5u.com熱心網友回復：
樓主，最后怎么解決的uj5u.com熱心網友回復：
看例外堆疊at com.servlet.IndexServlet.service(IndexServlet.java:67)，沒找到你的service方法，Failed at: #list foods as food [in template "index.ftl" at line 3, column 9]這行資訊，我英文不好，是不是foods和food的問題，模板和代碼中欄位沒對上
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標籤：Java EE