深入Spring Boot:实现对Fat Jar jsp的支持

spring boot 对于jsp支持的限制

对于jsp的支持,Spring Boot官方只支持了war的打包方式,不支持fat jar。参考官方文档: https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-developing-web-applications.html#boot-features-jsp-limitations

这里spring boot官方说是tomcat的问题,实际上是spring boot自己改变了打包格式引起的。参考之前的文章:http://hengyunabc.github.io/spring-boot-classloader/#spring-boot-1-3-%E5%92%8C-1-4-%E7%89%88%E6%9C%AC%E7%9A%84%E5%8C%BA%E5%88%AB

原来的结构之下,tomcat是可以扫描到fat jar里的META-INF/resources目录下面的资源的。在增加了BOOT-INF/classes之后,则tomcat扫描不到了。

那么怎么解决这个问题呢?下面给出一种方案,来实现对spring boot fat jar/exploded directory的jsp的支持。

个性化配置tomcat,把BOOT-INF/classes 加入tomcat的ResourceSet

在tomcat里,所有扫描到的资源都会放到所谓的ResourceSet里。比如servlet 3规范里的应用jar包的META-INF/resources就是一个ResourceSet

现在需要想办法把spring boot打出来的fat jar的BOOT-INF/classes目录加到ResourceSet里。

下面通过实现tomcat的 LifecycleListener接口,在Lifecycle.CONFIGURE_START_EVENT事件里,获取到BOOT-INF/classes的URL,再把这个URL加入到WebResourceSet里。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
/**
* Add main class fat jar/exploded directory into tomcat ResourceSet.
*
* @author hengyunabc 2017-07-29
*
*/
public class StaticResourceConfigurer implements LifecycleListener {

private final Context context;

StaticResourceConfigurer(Context context) {
this.context = context;
}

@Override
public void lifecycleEvent(LifecycleEvent event) {
if (event.getType().equals(Lifecycle.CONFIGURE_START_EVENT)) {
URL location = this.getClass().getProtectionDomain().getCodeSource().getLocation();

if (ResourceUtils.isFileURL(location)) {
// when run as exploded directory
String rootFile = location.getFile();
if (rootFile.endsWith("/BOOT-INF/classes/")) {
rootFile = rootFile.substring(0, rootFile.length() - "/BOOT-INF/classes/".length() + 1);
}
if (!new File(rootFile, "META-INF" + File.separator + "resources").isDirectory()) {
return;
}

try {
location = new File(rootFile).toURI().toURL();
} catch (MalformedURLException e) {
throw new IllegalStateException("Can not add tomcat resources", e);
}
}

String locationStr = location.toString();
if (locationStr.endsWith("/BOOT-INF/classes!/")) {
// when run as fat jar
locationStr = locationStr.substring(0, locationStr.length() - "/BOOT-INF/classes!/".length() + 1);
try {
location = new URL(locationStr);
} catch (MalformedURLException e) {
throw new IllegalStateException("Can not add tomcat resources", e);
}
}
this.context.getResources().createWebResourceSet(ResourceSetType.RESOURCE_JAR, "/", location,
"/META-INF/resources");

}
}
}

为了让spring boot embedded tomcat加载这个 StaticResourceConfigurer,还需要一个EmbeddedServletContainerCustomizer的配置:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
@Configuration
@ConditionalOnProperty(name = "tomcat.staticResourceCustomizer.enabled", matchIfMissing = true)
public class TomcatConfiguration {
@Bean
public EmbeddedServletContainerCustomizer staticResourceCustomizer() {
return new EmbeddedServletContainerCustomizer() {
@Override
public void customize(ConfigurableEmbeddedServletContainer container) {
if (container instanceof TomcatEmbeddedServletContainerFactory) {
((TomcatEmbeddedServletContainerFactory) container)
.addContextCustomizers(new TomcatContextCustomizer() {
@Override
public void customize(Context context) {
context.addLifecycleListener(new StaticResourceConfigurer(context));
}
});
}
}

};
}
}

这样子的话,spring boot就可以支持fat jar里的jsp资源了。

demo地址: https://github.com/hengyunabc/spring-boot-fat-jar-jsp-sample

总结

  • spring boot改变了打包结构,导致tomcat没有办法扫描到fat jar里的/BOOT-INF/classes
  • 通过一个StaticResourceConfigurer把fat jar里的/BOOT-INF/classes加到tomcat的ResourceSet来解决问题
横云断岭/hengyunabc wechat
欢迎您扫一扫上面的微信公众号,订阅横云断岭的专栏