springcloud与hystrix整合时freemarker依赖问题分析 - 文章 - 开发者社区

springcloud 整合 hystrix-dashboard 时出现报错信息，现针对问题的解决方法进行如下记录。

错误信息


      1. `freemarker.core._MiscTemplateException: Template importing failed (for parameter value "/spring.ftl"):`
2. `Syntax error in template "spring.ftl" in line 1, column 7:`
3. `Unknown FTL header parameter: output_format`
4. 
5. `----`
6. `FTL stack trace ("~" means nesting-related):`
7. `- Failed at: #import "/spring.ftl" as spring [in template "hystrix/index.ftl" at line 1, column 1]`
8. `----`
9. `at freemarker.core.LibraryLoad.accept(LibraryLoad.java:64) ~[freemarker-2.3.23.jar:2.3.23]`
10. `at freemarker.core.Environment.visit(Environment.java:324) [freemarker-2.3.23.jar:2.3.23]`
11. `at freemarker.core.MixedContent.accept(MixedContent.java:54) [freemarker-2.3.23.jar:2.3.23]`
12. `at freemarker.core.Environment.visit(Environment.java:324) [freemarker-2.3.23.jar:2.3.23]`
13. `at freemarker.core.Environment.process(Environment.java:302) [freemarker-2.3.23.jar:2.3.23]`
14. `at freemarker.template.Template.process(Template.java:325) [freemarker-2.3.23.jar:2.3.23]`
15. `at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:389) [spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
16. `at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:302) [spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
17. `at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:253) [spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
18. `at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:178) [spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
19. `at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316) [spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
20. `at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1371) [spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
21. `at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1117) [spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
22. `at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1056) [spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
23. `at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) [spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
24. `at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) [spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
25. `at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897) [spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
26. `at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) [tomcat-embed-core-9.0.24.jar:9.0.24]`
27. `at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882) [spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
28. `at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) [tomcat-embed-core-9.0.24.jar:9.0.24]`
29. `at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-9.0.24.jar:9.0.24]`
30. `at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.24.jar:9.0.24]`
31. `at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) [tomcat-embed-websocket-9.0.24.jar:9.0.24]`
32. `at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.24.jar:9.0.24]`
33. `at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.24.jar:9.0.24]`
34. `at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) [spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
35. `at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118) [spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
36. `at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.24.jar:9.0.24]`
37. `at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.24.jar:9.0.24]`
38. `at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92) [spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
39. `at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118) [spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
40. `at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.24.jar:9.0.24]`
41. `at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.24.jar:9.0.24]`
42. `at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) [spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
43. `at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118) [spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
44. `at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.24.jar:9.0.24]`
45. `at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.24.jar:9.0.24]`
46. `at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) [spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
47. `at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118) [spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]`
48. `at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.24.jar:9.0.24]`
49. `at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.24.jar:9.0.24]`
50. `at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) [tomcat-embed-core-9.0.24.jar:9.0.24]`
51. `at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.24.jar:9.0.24]`
52. `at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:526) [tomcat-embed-core-9.0.24.jar:9.0.24]`
53. `at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.24.jar:9.0.24]`
54. `at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.24.jar:9.0.24]`
55. `at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.24.jar:9.0.24]`
56. `at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.24.jar:9.0.24]`
57. `at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.24.jar:9.0.24]`
58. `at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.24.jar:9.0.24]`
59. `at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860) [tomcat-embed-core-9.0.24.jar:9.0.24]`
60. `at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1587) [tomcat-embed-core-9.0.24.jar:9.0.24]`
61. `at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.24.jar:9.0.24]`
62. `at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_121]`
63. `at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_121]`
64. `at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.24.jar:9.0.24]`
65. `at java.lang.Thread.run(Thread.java:745) [na:1.8.0_121]`
66. `Caused by: freemarker.core.ParseException: Syntax error in template "spring.ftl" in line 1, column 7:`
67. `Unknown FTL header parameter: output_format`
68. `at freemarker.core.FMParser.HeaderElement(FMParser.java:3374) ~[freemarker-2.3.23.jar:2.3.23]`
69. `at freemarker.core.FMParser.Root(FMParser.java:3428) ~[freemarker-2.3.23.jar:2.3.23]`
70. `at freemarker.template.Template.<init>(Template.java:208) [freemarker-2.3.23.jar:2.3.23]`
71. `at freemarker.cache.TemplateCache.loadTemplate(TemplateCache.java:495) ~[freemarker-2.3.23.jar:2.3.23]`
72. `at freemarker.cache.TemplateCache.getTemplate(TemplateCache.java:409) ~[freemarker-2.3.23.jar:2.3.23]`
73. `at freemarker.cache.TemplateCache.getTemplate(TemplateCache.java:261) ~[freemarker-2.3.23.jar:2.3.23]`
74. `at freemarker.template.Configuration.getTemplate(Configuration.java:1786) ~[freemarker-2.3.23.jar:2.3.23]`
75. `at freemarker.core.Environment.getTemplateForInclusion(Environment.java:2044) [freemarker-2.3.23.jar:2.3.23]`
76. `at freemarker.core.Environment.getTemplateForInclusion(Environment.java:1993) [freemarker-2.3.23.jar:2.3.23]`
77. `at freemarker.core.Environment.getTemplateForImporting(Environment.java:2112) [freemarker-2.3.23.jar:2.3.23]`
78. `at freemarker.core.LibraryLoad.accept(LibraryLoad.java:62) ~[freemarker-2.3.23.jar:2.3.23]`

乍一看，是 freemarker 解析的问题，但是所有的依赖都是正常情况下处理的，没有头绪。

解决方式

最先想到的是版本依赖的问题，于是查看 pom 依赖信息如下:


      1. `<parent>`
2. `<artifactId>AA-Platform</artifactId>`
3. `<groupId>com.aa</groupId>`
4. `<version>1.0-SNAPSHOT</version>`
5. `</parent>`
6. `<modelVersion>4.0.0</modelVersion>`
7. 
8. `<artifactId>AA-Hystrix</artifactId>`
9. 
10. `<dependencies>`
11. `<dependency>`
12. `<groupId>org.springframework.cloud</groupId>`
13. `<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>`
14. `</dependency>`
15. `<dependency>`
16. `<groupId>com.netflix.hystrix</groupId>`
17. `<artifactId>hystrix-javanica</artifactId>`
18. `<version>RELEASE</version>`
19. `</dependency>`
20. `<dependency>`
21. `<groupId>org.springframework.cloud</groupId>`
22. `<artifactId>spring-cloud-netflix-hystrix-dashboard</artifactId>`
23. `</dependency>`
24. `<dependency>`
25. `<groupId>org.springframework.cloud</groupId>`
26. `<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>`
27. `</dependency>`
28. `</dependencies>`

依赖树的信息如下:

picture.image

看到这里仍然没有头绪，因为像 freemarker 和 hystrix 的依赖都不缺少，也没有重复依赖，看不出依赖冲突。

后来突然想到在 eureka 的 server 端也有用到 freemarker 的情况，赶紧查看它的 pom 依赖如下:


      1. `<parent>`
2. `<groupId>org.springframework.boot</groupId>`
3. `<artifactId>spring-boot-starter-parent</artifactId>`
4. `<version>2.1.3.RELEASE</version>`
5. `<relativePath/> <!-- lookup parent from repository -->`
6. `</parent>`
7. `<modelVersion>4.0.0</modelVersion>`
8. 
9. `<artifactId>AA-EurekaService</artifactId>`
10. 
11. `<properties>`
12. `<java.version>1.8</java.version>`
13. `<spring-cloud.version>Greenwich.SR3</spring-cloud.version>`
14. `</properties>`
15. 
16. `<dependencies>`
17. `<dependency>`
18. `<groupId>org.springframework.cloud</groupId>`
19. `<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>`
20. `</dependency>`
21. 
22. `<dependency>`
23. `<groupId>org.springframework.boot</groupId>`
24. `<artifactId>spring-boot-starter-test</artifactId>`
25. `<scope>test</scope>`
26. `</dependency>`
27. `</dependencies>`
28. 
29. `<dependencyManagement>`
30. `<dependencies>`
31. `<dependency>`
32. `<groupId>org.springframework.cloud</groupId>`
33. `<artifactId>spring-cloud-dependencies</artifactId>`
34. `<version>${spring-cloud.version}</version>`
35. `<type>pom</type>`
36. `<scope>import</scope>`
37. `</dependency>`
38. `</dependencies>`
39. `</dependencyManagement>`

它的依赖树为:

picture.image

仔细比对，发现 spring-boot-starter-freemarker 的版本及 freemarker 的版本是不同的，在 AA-Hystrix 工程中 freemarker 的依赖为 2.3.23，但是在 AA-EurekaService 工程中 freemarker 的依赖为 2.3.29，于是在 AA-Hystrix 项目中将 freemarker 的依赖版本替换成 2.3.29(排除低版本的依赖，重新引入高版本的依赖)，问题解决。

虽然问题解决了，但是还是存在很大的疑惑。

具体分析

为什么在同一个父工程中，两个子 Module 表现出的版本依赖不一致？

我们先来看下整个 AA 项目的父 pom 中的依赖，这里我们只列举与本文相关的主要依赖:


      1. `<properties>`
2. `<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>`
3. `<maven.compiler.source>1.8</maven.compiler.source>`
4. `<maven.compiler.target>1.8</maven.compiler.target>`
5. `<spring.boot.parent.version>2.1.8.RELEASE</spring.boot.parent.version>`
6. `<freemarker.version>2.3.23</freemarker.version>`
7. `</properties>`
8. 
9. `<dependencyManagement>`
10. `<dependency>`
11. `<groupId>org.springframework.cloud</groupId>`
12. `<artifactId>spring-cloud-dependencies</artifactId>`
13. `<version>Greenwich.SR3</version>`
14. `<type>pom</type>`
15. `<scope>import</scope>`
16. `</dependency>`
17. `<dependency>`
18. `<groupId>org.springframework.boot</groupId>`
19. `<artifactId>spring-boot-starter-parent</artifactId>`
20. `<version>${spring.boot.parent.version}</version>`
21. `<type>pom</type>`
22. `<scope>import</scope>`
23. `</dependency>`
24. `</dependencyManagement>`
25. `<dependency>`
26. `<groupId>org.springframework.boot</groupId>`
27. `<artifactId>spring-boot-starter</artifactId>`
28. `</dependency>`
29. `<dependency>`
30. `<groupId>org.springframework.boot</groupId>`
31. `<artifactId>spring-boot-starter-test</artifactId>`
32. `<scope>test</scope>`
33. `</dependency>`

由 pom 可以看出，父 pom 中 spring-boot-starter-parent 的依赖版本号为 2.1.8.RELEASE，spring-cloud-dependencies 的依赖版本为 Greenwich.SR3 对应的版本号为 2.1.3.RELEASE

因为在 AA-EurekaService 只依赖了父 pom 的 spring-boot-starter，没有依赖父 pom 的 dependencyManagement 中的其他依赖(如 freemarker 的依赖)。它的 parent 为:


      1. `<parent>`
2. `<groupId>org.springframework.boot</groupId>`
3. `<artifactId>spring-boot-starter-parent</artifactId>`
4. `<version>2.1.3.RELEASE</version>`
5. `<relativePath/> <!-- lookup parent from repository -->`
6. `</parent>`

因为依赖了外层 pom 的 spring-boot-statrer 的 2.1.8.RELEASE 版本，所以它的 spring-boot-starter-freemarker 的依赖是 2.1.8.RELEASE，但是它 freemarker 的依赖是由 2.1.8.RELEASE 版本的 spring-boot-starter-freemarker 依赖的 2.3.29 版本。

而在 AA-Hystrix 项目中，完全继承了父 pom，包括 freemarker 的版本，所以依赖的 freemarker 为父 pom 的 dependencyManagement 中配置的 2.3.23 版本。

究其原因是这是一个组内关于 springcloud 的试验性项目，很多 module 为不同成员创建，没有按父 module 规范处理，从而引起了依赖配置的混乱。而关于 freemarker 的版本问题则是对 springboot 进行升级后，一些对应的依赖包也需要进行升级，否则就会出现问题。

最后的解决方法

父 pom 修改

将父 pom 中的 freemarker 版本号修改成 2.3.29

AA-EurekaService 的修改

pom 中的 parent 修改成如下:


      1. `<parent>`
2. `<artifactId>AA-Platform</artifactId>`
3. `<groupId>com.aa</groupId>`
4. `<version>1.0-SNAPSHOT</version>`
5. `</parent>`