springboot整合freemarker踩坑

報(bào)錯(cuò)

2021-04-23 02:01:18.148 ERROR 9484 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> hots  [in template "inc/right.ftl" at line 6, column 11]

----
Tip: If the failing expression is known to 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: @hots  [in template "inc/right.ftl" at line 6, column 9]
    - Reached through: #include "/inc/right.ftl"  [in template "index.ftl" at line 52, column 13]
    ~ Reached through: #nested  [in template "inc/layout.ftl" in macro "layout" at line 25, column 5]
    ~ Reached through: @layout "首頁(yè)"  [in template "index.ftl" at line 2, column 1]
----] with root cause

freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> hots  [in template "inc/right.ftl" at line 6, column 11]

----
Tip: If the failing expression is known to 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: @hots  [in template "inc/right.ftl" at line 6, column 9]
    - Reached through: #include "/inc/right.ftl"  [in template "index.ftl" at line 52, column 13]
    ~ Reached through: #nested  [in template "inc/layout.ftl" in macro "layout" at line 25, column 5]
    ~ Reached through: @layout "首頁(yè)"  [in template "index.ftl" at line 2, column 1]
----
    at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134) ~[freemarker-2.3.28.jar:2.3.28]
    at freemarker.core.UnifiedCall.accept(UnifiedCall.java:106) ~[freemarker-2.3.28.jar:2.3.28]
    at freemarker.core.Environment.visit(Environment.java:330) ~[freemarker-2.3.28.jar:2.3.28]
    at freemarker.core.Environment.visit(Environment.java:336) ~[freemarker-2.3.28.jar:2.3.28]
    at freemarker.core.Environment.include(Environment.java:2582) ~[freemarker-2.3.28.jar:2.3.28]
    at freemarker.core.Include.accept(Include.java:171) ~[freemarker-2.3.28.jar:2.3.28]
    at freemarker.core.Environment.visit(Environment.java:366) ~[freemarker-2.3.28.jar:2.3.28]
    at freemarker.core.Environment.invokeNestedContent(Environment.java:618) ~[freemarker-2.3.28.jar:2.3.28]
    at freemarker.core.BodyInstruction.accept(BodyInstruction.java:60) ~[freemarker-2.3.28.jar:2.3.28]
    at freemarker.core.Environment.visit(Environment.java:366) ~[freemarker-2.3.28.jar:2.3.28]
    at freemarker.core.Environment.invoke(Environment.java:775) ~[freemarker-2.3.28.jar:2.3.28]
    at freemarker.core.UnifiedCall.accept(UnifiedCall.java:83) ~[freemarker-2.3.28.jar:2.3.28]
    at freemarker.core.Environment.visit(Environment.java:330) ~[freemarker-2.3.28.jar:2.3.28]
    at freemarker.core.Environment.visit(Environment.java:336) ~[freemarker-2.3.28.jar:2.3.28]
    at freemarker.core.Environment.process(Environment.java:309) ~[freemarker-2.3.28.jar:2.3.28]
    at freemarker.template.Template.process(Template.java:384) ~[freemarker-2.3.28.jar:2.3.28]
    at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:389) ~[spring-webmvc-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:302) ~[spring-webmvc-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:253) ~[spring-webmvc-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:178) ~[spring-webmvc-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316) ~[spring-webmvc-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1370) ~[spring-webmvc-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1116) ~[spring-webmvc-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1055) ~[spring-webmvc-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) ~[spring-webmvc-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897) ~[spring-webmvc-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882) ~[spring-webmvc-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.14.jar:9.0.14]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92) ~[spring-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:834) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1417) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) ~[na:na]
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) ~[na:na]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.14.jar:9.0.14]
    at java.base/java.lang.Thread.run(Thread.java:834) ~[na:na]

2021-04-23 02:01:18.177 ERROR 9484 --- [nio-8080-exec-1] s.e.ErrorMvcAutoConfiguration$StaticView : Cannot render error page for request [/] and exception [The following has evaluated to null or missing:
==> hots  [in template "inc/right.ftl" at line 6, column 11]

----
Tip: If the failing expression is known to 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: @hots  [in template "inc/right.ftl" at line 6, column 9]
    - Reached through: #include "/inc/right.ftl"  [in template "index.ftl" at line 52, column 13]
    ~ Reached through: #nested  [in template "inc/layout.ftl" in macro "layout" at line 25, column 5]
    ~ Reached through: @layout "首頁(yè)"  [in template "index.ftl" at line 2, column 1]
----] as the response has already been committed. As a result, the response may have the wrong status code.

問(wèn)題原因

因?yàn)樵趕ervice里試著把redis邏輯代碼運(yùn)行，然后再控制臺(tái)上輸出，結(jié)果發(fā)現(xiàn)結(jié)果是沒(méi)有問(wèn)題的，而且通過(guò)報(bào)錯(cuò)信息初步認(rèn)為是前端的問(wèn)題，hots沒(méi)找到，但是跟之前的一個(gè)類(lèi)似功能相比較，然后通過(guò)不斷的對(duì)比，找到問(wèn)題是出在配置類(lèi)。

之前一直認(rèn)為template類(lèi)中的getname方法就能完成映射功能

其實(shí)需要在FreemarkerConfig類(lèi)里面進(jìn)行聲明

解決方法

再FreemarkerConfig類(lèi)先通過(guò)@Autowired導(dǎo)入template類(lèi)，然后使用configuration.setSharedVariable(“hots”, hotsTemplate);進(jìn)行聲明，缺少這一步會(huì)使得前端對(duì)于<@hots>這個(gè)標(biāo)簽無(wú)法識(shí)別。

springboot freemarker基礎(chǔ)配置及使用

1.基礎(chǔ)配置

1.1引入依賴(lài)

<!-- 引入freemarker模板引擎的依賴(lài) -->
<dependency>
? ? <groupId>org.springframework.boot</groupId>
? ? <artifactId>spring-boot-starter-freemarker</artifactId>
</dependency>

1.2在application.properties配置文件中添加如下配置：

# 是否開(kāi)啟thymeleaf緩存,本地為false，生產(chǎn)建議為true
spring.freemarker.cache=false
spring.freemarker.charset=UTF-8
spring.freemarker.allow-request-override=false
spring.freemarker.check-template-location=true
#類(lèi)型
spring.freemarker.content-type=text/html
spring.freemarker.expose-request-attributes=true
spring.freemarker.expose-session-attributes=true
#
#文件后綴
spring.freemarker.suffix=.ftl
#路徑 .ftl文件就創(chuàng)建在templates下面或者子目錄
spring.freemarker.template-loader-path=classpath:/templates/

2.基礎(chǔ)使用

首先我在controller類(lèi)中編寫(xiě)一個(gè)測(cè)試接口用來(lái)測(cè)試使用，編寫(xiě)內(nèi)容如下

@Controller
public class FreeMarkerController {

? ? Map<String ,Object> map = new HashMap<>();
? ? List<Object> list = new ArrayList();
? ? @GetMapping("/freemaker/{id}/{name}")
? ? public String demo(@PathVariable("id")String id ,@PathVariable("name") String name,Model model){

? ? ? ? map.clear();
? ? ? ? map.put("id",id);
? ? ? ? map.put("name",name);
? ? ? ? list.add(2);
? ? ? ? list.add(4);
? ? ? ? map.put("aa",null);
? ? ? ? model.addAttribute("map",map);
? ? ? ? model.addAttribute("list",list);
? ? ? ? model.addAttribute("date",new Date());
? ? ? ? return "index";
? ? }
}

以下所有變量都是有上面接口提供

2.1調(diào)用map類(lèi)型數(shù)據(jù),實(shí)體類(lèi)也可使用此格式調(diào)用屬性

/*可直接獲取id對(duì)應(yīng)的v值*/
id:${map.id}
name:${map.name}

2.2集合調(diào)用，set集合也可用此格式調(diào)用相應(yīng)的元素

list01:${list[0]}
list02:${list[1]}

2.3字符串拼接的兩種方法

${"你好啊${map.name}"}
${"你好啊"+map.name}

2.4FreeMarker表達(dá)式中支持“+”、“－”、“*”、“/”、“%”運(yùn)算符

${list[1]+list[0]}
${list[1]-list[0]}
${list[1]*list[0]}
${list[1]/list[0]}
${list[1]%list[0]}

2.5表達(dá)式中支持的比較運(yùn)算符有如下幾種：

1. =（或者==）：判斷兩個(gè)值是否相等；
2. !=：判斷兩個(gè)值是否不相等；
注： =和!=可以用作字符串、數(shù)值和日期的比較，但兩邊的數(shù)據(jù)類(lèi)型必須相同。而且FreeMarker的比較是精確比較，不會(huì)忽略大小寫(xiě)及空格。
3. >（或者gt）：大于
4. >=（或者gte）：大于等于
5. <（或者lt）：小于
6. <=（或者lte）：小于等于
注： 上面這些比較運(yùn)算符可以用于數(shù)字和日期，但不能用于字符串。大部分時(shí)候，使用gt比>有更好的效果，因?yàn)镕reeMarker會(huì)把>解釋成標(biāo)簽的結(jié)束字符。可以使用括號(hào)來(lái)避免這種

2.6時(shí)間格式轉(zhuǎn)換

${date?string("yyyy-MM-dd")}

2.7支持邏輯表達(dá)式

FreeMarker支持邏輯運(yùn)算但是只支持布爾型邏輯運(yùn)算兩個(gè)值進(jìn)行比較運(yùn)算的的時(shí)候需要添加括號(hào)才能進(jìn)行邏輯運(yùn)算,一般用于指令中

FreeMarker支持邏輯運(yùn)算但是只支持布爾型邏輯運(yùn)算兩個(gè)值進(jìn)行比較運(yùn)算的的時(shí)候需要添加括號(hào)才能進(jìn)行邏輯運(yùn)算,一般用于指令中
1. &&： 邏輯與；
2. ||：邏輯或；
3. !：邏輯非
邏輯運(yùn)算符只能用于布爾值。

2.8FreeMarker無(wú)法理解null值

FreeMarker的變量必須賦值，否則就會(huì)拋出異常。而對(duì)于FreeMarker來(lái)說(shuō)，null值和不存在的變量是完全一樣的，因?yàn)镕reeMarker無(wú)法理解null值。
FreeMarker提供兩個(gè)運(yùn)算符來(lái)避免空值：
1.!運(yùn)算
1.1若是msg不存在不報(bào)異常默認(rèn)空值，若是不使用！會(huì)報(bào)異常<br>
${msg!}
1.2若是存在則輸出，若是不存在則默認(rèn)為abc<br>
${map.a!"abc"}<br>
2.？？返回布爾值一般用在指令中下面會(huì)有引用此處不解釋<br>

2.9 if指令

<#if map.aa?? >
? ? 存在
? ? <#else >
? ? 不存在
</#if>
<br>
<#if (list[0]>=3) >
? ? 優(yōu)秀
? ? <#elseif (list[0]>=2)>
? ? 良好
? ? <#else >
? ? 差勁
</#if>

2.10 list指令 遍歷

<#list list as li>
? ? ${li}<br>
</#list>

以上為個(gè)人經(jīng)驗(yàn)，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。

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