Freemarker 入门报错（网上的文章，都没有出现博主这种情况么）

本地写了一个很简单的Freemarker 测试，从对象属性中获取值，替换模版，然后打印出来。

本以为非常简单的一个测试，结果愣是没出结果，一直在报错。

各种百度、谷歌，愣是没有我这种情况。

冥冥之中，自有天助。记录下错误和结论。

奉天承运，皇帝昭曰：上代码！

package tdd.com.ilvf.common.util;

import java.io.StringWriter;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

import com.ilvf.common.util.DateUtil;

import freemarker.cache.StringTemplateLoader;
import freemarker.template.Configuration;
import freemarker.template.Template;

public class FreemarkerTest {
	public static void main(String[] args) throws Exception {
		//注意版本与pom中的引用版本一致
		Configuration cfg = new Configuration(Configuration.VERSION_2_3_23);
		cfg.setDefaultEncoding("utf-8");
		StringTemplateLoader stringTemplateLoader = new StringTemplateLoader();
		cfg.setTemplateLoader(stringTemplateLoader);
		String templateContent="欢迎：${name}, 生日:${birth?string('yyyy-MM-dd')},你的身份证号码是${card.name}";
		stringTemplateLoader.putTemplate("myTemplate", templateContent);
		Template template = cfg.getTemplate("myTemplate");
		
		Map<String, Object> dataMap = new HashMap<String, Object>();
		dataMap.put("name", "张三");
		dataMap.put("birth", DateUtil.addMonth(new Date(), -1));
		dataMap.put("card", new Card("Audi", "123456789"));
		
		StringWriter writer = new StringWriter();  
		template.process(dataMap, writer);
		System.out.println(writer.toString());  
	}
}

class Card {
	private String name;
	private String number;
	
	public Card(String name, String number) {
		this.name = name;
		this.number = number;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getNumber() {
		return number;
	}
	public void setNumber(String number) {
		this.number = number;
	}
	@Override
	public String toString() {
		return "Card["+name+","+number+"]";
	}
}

pom版本为
<dependency>
           <groupId>org.freemarker</groupId>
           <artifactId>freemarker</artifactId>
           <version>2.3.23</version>
       </dependency>

执行后，报错如下：

2019-03-22 15:39:27 [ main:0 ] - [ ERROR ] freemarker.log._Log4jLoggerFactory$Log4jLogger.error(_Log4jLoggerFactory.java:60) Error executing FreeMarker template
FreeMarker template error:
The following has evaluated to null or missing:
==> card.name [in template "myTemplate" at line 1, column 56]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
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: ${card.name} [in template "myTemplate" at line 1, column 54]
----

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.EvalUtil.coerceModelToString(EvalUtil.java:355)
   at freemarker.core.Expression.evalAndCoerceToString(Expression.java:82)
   at freemarker.core.DollarVariable.accept(DollarVariable.java:41)
   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 tdd.com.ilvf.common.util.FreemarkerTest.main(FreemarkerTest.java:35)
Exception in thread "main" FreeMarker template error:
The following has evaluated to null or missing:
==> card.name [in template "myTemplate" at line 1, column 56]

----
FTL stack trace ("~" means nesting-related):
- Failed at: ${card.name} [in template "myTemplate" at line 1, column 54]
----

确认检查过类名、属性名、getter、setter方法，也确定属性已经赋值，没有null。

结论：无意中，将 Card类放到单独的文件中（除此之外，无任何改动），运行正常。

Freemarker 入门 报错（网上的文章，都没有出现博主这种情况么）

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