java为什么我在传递给freemarker的哈希映射上得到一个null值，而它不是null？
public static void main(String[] args) throws IOException {
port(8080);
Configuration config = new Configuration(Configuration.VERSION_2_3_26);
config.setDirectoryForTemplateLoading(new File("PATH_NAME"));
get("/test", (req,res) ->{
StringWriter writer = new StringWriter();
Template temp = config.getTemplate("loginform.ftl");
temp.process(null, writer);
return writer;
});
post("/select", (req,res) -> {
String city = req.queryParams("city");
String state = req.queryParams("state");
Map<String, Object> data = new HashMap<>();
data.put("Hello", "Your not null!");
StringWriter writer = new StringWriter();
Template temp = config.getTemplate("result.ftl");
temp.process(data, writer);
return writer;
});
}
以上是我正在开发的Spark应用程序的主要方法。它包括两个模板，loginform。ftl和结果。ftl。登录表单。ftl是一个简单的html表单，它向服务器发送post请求，由上面代码中的post处理程序处理。当我填写表单并发送请求时，我得到一个500内部服务器错误。错误与结果有关。ftl，现在，我用它来测试模板制作。我正在将哈希映射传递给结果。ftl模板。我得到的错误是：
FreeMarker template error:
The following has evaluated to null or missing:
==> data [in template "result.ftl" at line 2, column 8]
FTL stack trace ("~" means nesting-related):
- Failed at: #list data as key, value [in template "result.ftl" at line
2, column 1]
----
我认为这意味着生成模板时数据为空，但很明显不是。我不知道会发生这种情况。我的模板文件如下
登录表单。超光速
<form action= "/select" method= "POST" accept-charset="utf-8">
City Name: <input type= "text" name = "city">
State(2 letter format):<input type= "text" name = "state">
<input type= "submit" id = "submitButton">
</form>
结果。超光速
<html>
<#list data as key, value>
${key} = ${value};
</#list>
</html>
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