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Posted to notifications@shenyu.apache.org by xi...@apache.org on 2021/08/20 11:19:55 UTC
[incubator-shenyu-website] branch main updated: Add code analysis
for context-path plugin (#206)
This is an automated email from the ASF dual-hosted git repository.
xiaoyu pushed a commit to branch main
in repository https://gitbox.apache.org/repos/asf/incubator-shenyu-website.git
The following commit(s) were added to refs/heads/main by this push:
new b98ae9f Add code analysis for context-path plugin (#206)
b98ae9f is described below
commit b98ae9f27c4eeb1639c4401a9ee0068160dd8c08
Author: Kunshuai Zhu <jo...@gmail.com>
AuthorDate: Fri Aug 20 06:19:48 2021 -0500
Add code analysis for context-path plugin (#206)
* Add code analysis for context-path plugin
* Refactor name of images
---
.../code-analysis-context-path-plugin/index.md | 115 +++++++++++++++++++++
.../context-path-404.png | Bin 0 -> 22216 bytes
.../context-path-RequestMapping.png | Bin 0 -> 26804 bytes
.../context-path-rules-with-prefix.png | Bin 0 -> 40427 bytes
.../context-path-rules-without-prefix.png | Bin 0 -> 44052 bytes
.../context-path-success.png | Bin 0 -> 35625 bytes
6 files changed, 115 insertions(+)
diff --git a/content/zh/blog/code-analysis-context-path-plugin/index.md b/content/zh/blog/code-analysis-context-path-plugin/index.md
new file mode 100644
index 0000000..93a58e9
--- /dev/null
+++ b/content/zh/blog/code-analysis-context-path-plugin/index.md
@@ -0,0 +1,115 @@
+---
+author: "Kunshuai Zhu"
+authorlink: "https://github.com/JooKS-me"
+date: 2021-08-20T11:00:00.000Z
+title: "ShenYu Context-Path插件源码分析"
+tags: ["Plugin", "ShenYu", "GateWay"]
+cover: "/img/activities/apache-open-shenyu-02.jpg"
+descripton: "ShenYu Context-Path插件源码分析"
+---
+
+## Demo跑起来
+
+1. 启动ShenYu Admin
+
+2. 启动ShenYu Bootstrap
+
+3. 修改一下shenyu-examples-http（我们这里直接用shenyu的example）
+
+ **在HttpTestController.java中，将类注解@RequestMapping的path值稍作修改**，改成`"/v1/test"`，如下图所示。
+
+ 
+
+4. 启动shenyu-examples-http
+
+到这里，我们的服务就都起来了。
+
+然后我们请求接口 `http://localhost:9195/http/test/findByUserId?userId=1001` ，结果返回404。
+
+
+
+我们分析一下网关处理这个请求的过程的流程：
+
+1. 请求网关的 `/http/test/findByUserId`
+
+2. 经过各种插件的处理。。。
+
+3. 然后到了context_path插件。
+
+ 我们可以在admin里面发现有这样一条规则，将contextPath设置为`/http`，addPrefix设置为空。实际上，这样的设置使得shenyu在向目标服务发送请求前，将请求路径中的`/http`替换成了`空`。(详细内容见后续的源码分析)
+
+ 
+
+那么你现在应该知道了，我们只需要在addPrefix的空格里填上`/v1`就能正确地请求到目标服务了！
+
+
+
+
+
+## 分析源码
+
+首先，看`ContextPathPlugin#doExecute`方法，这是这个插件的核心。
+
+```java
+protected Mono<Void> doExecute(final ServerWebExchange exchange, final ShenyuPluginChain chain, final SelectorData selector, final RuleData rule) {
+ ...
+ // 1. 从JVM缓存中取得contextMappingHandle
+ ContextMappingHandle contextMappingHandle = ContextPathPluginDataHandler.CACHED_HANDLE.get().obtainHandle(CacheKeyUtils.INST.getKey(rule));
+ ...
+ // 2. 根据contextMappingHandle设置shenyu上下文
+ buildContextPath(shenyuContext, contextMappingHandle);
+ return chain.execute(exchange);
+}
+```
+
+1. 从JVM缓存中取得`contextMappingHandle`
+
+ 这里的`contextMappingHandle`是`ContextMappingHandle`类的实例，里面有两个成员变量：`contextPath`和`addPrefix`
+
+ 这两个变量在之前Admin里面的Rules表单里有出现过，是在数据同步的时候更新的。
+
+2. 根据contextMappingHandle设置shenyu上下文
+
+ 下面是`ContextPathPlugin#buildContextPath`方法的源代码
+
+ ```java
+ private void buildContextPath(final ShenyuContext context, final ContextMappingHandle handle) {
+ String realURI = "";
+ // 1. 设置shenyu的context path，根据contextPath的长度将真实URI的前缀去掉
+ if (StringUtils.isNoneBlank(handle.getContextPath())) {
+ context.setContextPath(handle.getContextPath());
+ context.setModule(handle.getContextPath());
+ realURI = context.getPath().substring(handle.getContextPath().length());
+ }
+ // 加上前缀
+ if (StringUtils.isNoneBlank(handle.getAddPrefix())) {
+ if (StringUtils.isNotBlank(realURI)) {
+ realURI = handle.getAddPrefix() + realURI;
+ } else {
+ realURI = handle.getAddPrefix() + context.getPath();
+ }
+ }
+ context.setRealUrl(realURI);
+ }
+ ```
+
+ - 设置shenyu的context path，**根据contextPath的长度将真实URI的前缀去掉**
+
+ 你可能会有疑问，**这里所谓的「根据contextPath的长度」会不会有问题呢？**
+
+ 实际上这样的判断是没有问题的，因为请求在被Selector和Rules匹配到之后，才会被插件处理。所以在设置好Selector和Rules的前提下，是完全可以满足转换特定contextPath的需求的。
+
+然后，`ContextPathPlugin`类还有一个比较重要的方法`skip`，下面展示了部分代码。我们可以发现：**如果是对RPC服务的调用，就会直接跳过context_path插件。**
+
+```java
+public Boolean skip(final ServerWebExchange exchange) {
+ ...
+ return Objects.equals(rpcType, RpcTypeEnum.DUBBO.getName())
+ || Objects.equals(rpcType, RpcTypeEnum.GRPC.getName())
+ || Objects.equals(rpcType, RpcTypeEnum.TARS.getName())
+ || Objects.equals(rpcType, RpcTypeEnum.MOTAN.getName())
+ || Objects.equals(rpcType, RpcTypeEnum.SOFA.getName());
+}
+```
+
+最后，context_path插件还有另一个类`ContextPathPluginDataHandler`。这个类的作用是订阅插件的数据，当插件配置被修改、删除、增加时，就往JVM缓存里面修改、删除、新增数据。
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