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2023-08-06 20:48:54
本篇的知识点是bean的生命周期回调：在bean生命周期的不同阶段，都可以触发自定义代码的执行
触发自定义代码执行的具体方式，是用对应的注解去修饰要执行的方法，如下图所示：
有两种模式可以实现生命周期回调：拦截器模式和自定义模式，接下来通过编码依次学习
已详细介绍了quarkus拦截器的自定义和使用，包括以下三个步骤
如果要自定义bean的生命周期回调，也是遵照上述步骤执行，接下来编码实现
首先定义拦截器，名为TrackLifeCycle，就是个普通拦截器，需要用注解InterceptorBinding修饰
<span style="color:#393939"><span style="background-color:#faf7ef"><code class="language-java"><span style="color:#0000ff">package</span> com.bolingcavalry.interceptor.define;
<span style="color:#0000ff">import</span> javax.interceptor.InterceptorBinding;
<span style="color:#0000ff">import</span> java.lang.annotation.ElementType;
<span style="color:#0000ff">import</span> java.lang.annotation.Retention;
<span style="color:#0000ff">import</span> java.lang.annotation.RetentionPolicy;
<span style="color:#0000ff">import</span> java.lang.annotation.Target;
<span style="color:#0000ff">import</span> <span style="color:#0000ff">static</span> java.lang.annotation.ElementType.TYPE;
<span style="color:#2b91af">@InterceptorBinding</span>
<span style="color:#2b91af">@Target({TYPE, ElementType.METHOD})</span>
<span style="color:#2b91af">@Retention(RetentionPolicy.RUNTIME)</span>
<span style="color:#0000ff">public</span> <span style="color:#2b91af">@interface</span> TrackLifeCycle {
}
</code></span></span>然后是实现拦截器的功能，有几处要注意的地方稍后会提到
<span style="color:#393939"><span style="background-color:#faf7ef"><code class="language-java"><span style="color:#0000ff">package</span> com.bolingcavalry.interceptor.impl;
<span style="color:#0000ff">import</span> com.bolingcavalry.interceptor.define.TrackLifeCycle;
<span style="color:#0000ff">import</span> io.quarkus.arc.Priority;
<span style="color:#0000ff">import</span> io.quarkus.logging.Log;
<span style="color:#0000ff">import</span> javax.annotation.PostConstruct;
<span style="color:#0000ff">import</span> javax.annotation.PreDestroy;
<span style="color:#0000ff">import</span> javax.interceptor.AroundConstruct;
<span style="color:#0000ff">import</span> javax.interceptor.Interceptor;
<span style="color:#0000ff">import</span> javax.interceptor.InvocationContext;
<span style="color:#2b91af">@TrackLifeCycle</span>
<span style="color:#2b91af">@Interceptor</span>
<span style="color:#2b91af">@Priority(Interceptor.Priority.APPLICATION + 1)</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">class</span> <span style="color:#a31515">LifeCycleInterceptor</span> {
<span style="color:#2b91af">@AroundConstruct</span>
<span style="color:#0000ff">void</span> <span style="color:#a31515">execute</span>(InvocationContext context) <span style="color:#0000ff">throws</span> Exception {
Log.info(<span style="color:#a31515">"start AroundConstruct"</span>);
<span style="color:#0000ff">try</span> {
context.proceed();
} <span style="color:#0000ff">catch</span> (Exception e) {
e.printStackTrace();
}
Log.info(<span style="color:#a31515">"end AroundConstruct"</span>);
}
<span style="color:#2b91af">@PostConstruct</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span> <span style="color:#a31515">doPostConstruct</span>(InvocationContext ctx) {
Log.info(<span style="color:#a31515">"life cycle PostConstruct"</span>);
}
<span style="color:#2b91af">@PreDestroy</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span> <span style="color:#a31515">doPreDestroy</span>(InvocationContext ctx) {
Log.info(<span style="color:#a31515">"life cycle PreDestroy"</span>);
}
}
</code></span></span>上述代码有以下几点需要注意
用注解Interceptor和TrackLifeCycle修饰，说明这是拦截器TrackLifeCycle的实现
被拦截bean实例化的时候，AroundConstruct修饰的方法execute就会被执行，这和一文中的AroundInvoke的用法很相似
被拦截bean创建成功后，PostConstruct修饰的方法doPostConstruct就会被执行
被拦截bean在销毁之前，PreDestroy修饰的方法doPreDestroy就会被执行
接下来是使用拦截器TrackLifeCycle了，用于演示的bean如下，用TrackLifeCycle修饰，有构造方法和简单的helloWorld方法
<span style="color:#393939"><span style="background-color:#faf7ef"><code class="language-java"><span style="color:#2b91af">@ApplicationScoped</span>
<span style="color:#2b91af">@TrackLifeCycle</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">class</span> <span style="color:#a31515">Hello</span> {
<span style="color:#0000ff">public</span> <span style="color:#a31515">Hello</span>() {
Log.info(<span style="color:#0000ff">this</span>.getClass().getSimpleName() + <span style="color:#a31515">" at instance"</span>);
}
<span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span> <span style="color:#a31515">helloWorld</span>() {
Log.info(<span style="color:#a31515">"Hello world!"</span>);
}
}
</code></span></span>最后再写个单元测试类验证
<span style="color:#393939"><span style="background-color:#faf7ef"><code class="language-java"><span style="color:#2b91af">@QuarkusTest</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">class</span> <span style="color:#a31515">LifeCycleTest</span> {
<span style="color:#2b91af">@Inject</span>
Hello hello;
<span style="color:#2b91af">@Test</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span> <span style="color:#a31515">testLifyCycle</span>() {
hello.helloWorld();
}
}
</code></span></span>执行单元测试，控制台输出如下，可见拦截器的日志输出都符合预期
<span style="color:#393939"><span style="background-color:#faf7ef"><code class="language-shell">15:26:32,447 INFO [io.quarkus] (main) Quarkus 2.7.3.Final on JVM started in 2.899s. Listening on: http://localhost:8081 15:26:32,448 INFO [io.quarkus] (main) Profile test activated. 15:26:32,448 INFO [io.quarkus] (main) Installed features: [agroal, cdi, narayana-jta, resteasy, smallrye-context-propagation, vertx] 15:26:32,483 INFO [com.bol.lif.Hello] (main) Hello_ClientProxy at instance 15:26:33,040 INFO [com.bol.int.imp.LifeCycleInterceptor] (main) start AroundConstruct 15:26:33,040 INFO [com.bol.lif.Hello] (main) Hello_Subclass at instance 15:26:33,040 INFO [com.bol.int.imp.LifeCycleInterceptor] (main) end AroundConstruct 15:26:33,041 INFO [com.bol.int.imp.LifeCycleInterceptor] (main) life cycle PostConstruct 15:26:33,041 INFO [com.bol.lif.Hello] (main) Hello world! 15:26:33,097 INFO [com.bol.int.imp.LifeCycleInterceptor] (main) life cycle PreDestroy 15:26:33,128 INFO [io.quarkus] (main) Quarkus stopped in 0.075s </code></span></span>
以上就是通过拦截器制作的bean生命周期回调的全过程，接下来再看另一种方式：不用拦截器的方式
刚才的拦截器模式有个明显问题：如果不同bean的生命周期回调有不同业务需求，该如何是好？为每个bean做一个拦截器吗？随着bean的增加会有大量拦截器，似乎不是个好的方案
如果您熟悉spring，对下面的代码要改不陌生，这是来自的内容，直接在bean的方法上用PostConstruct和PreDestroy修饰，即可在bean的创建完成和销毁前被调用
<span style="color:#393939"><span style="background-color:#faf7ef"><code class="language-java"><span style="color:#0000ff">public</span> <span style="color:#0000ff">class</span> <span style="color:#a31515">CachingMovieLister</span> {
<span style="color:#2b91af">@PostConstruct</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span> <span style="color:#a31515">populateMovieCache</span>() {
<span style="color:#008000">// populates the movie cache upon initialization...</span>
}
<span style="color:#2b91af">@PreDestroy</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span> <span style="color:#a31515">clearMovieCache</span>() {
<span style="color:#008000">// clears the movie cache upon destruction...</span>
}
}
</code></span></span>实际上，quarkus也支持上述方式，不过和拦截器相比有两个差异：
在bean的内部，只能用PostConstruct和TrackLifeCycle，不能用AroundConstruct，只有拦截器才能用AroundConstruct
在拦截器中，PostConstruct和TrackLifeCycle修饰的方法必须要有InvocationContext类型的入参，但是在bean内部则没有此要求
咱们来改造Hello.java的源码，修改后如下，增加了两个方法，分别被PostConstruct和PreDestroy修饰
<span style="color:#393939"><span style="background-color:#faf7ef"><code class="language-java"><span style="color:#2b91af">@ApplicationScoped</span>
<span style="color:#2b91af">@TrackLifeCycle</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">class</span> <span style="color:#a31515">Hello</span> {
<span style="color:#0000ff">public</span> <span style="color:#a31515">Hello</span>() {
Log.info(<span style="color:#0000ff">this</span>.getClass().getSimpleName() + <span style="color:#a31515">" at instance"</span>);
}
<span style="color:#2b91af">@PostConstruct</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span> <span style="color:#a31515">doPostConstruct</span>() {
Log.info(<span style="color:#a31515">"at doPostConstruct"</span>);
}
<span style="color:#2b91af">@PreDestroy</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span> <span style="color:#a31515">doPreDestroy</span>() {
Log.info(<span style="color:#a31515">"at PreDestroy"</span>);
}
<span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span> <span style="color:#a31515">helloWorld</span>() {
Log.info(<span style="color:#a31515">"Hello world!"</span>);
}
}
</code></span></span>再次运行单元测试，控制台输出如下，可见Hello自定义的两个生命周期回调都执行了，同时原拦截器的三个回调也都正常执行
<span style="color:#393939"><span style="background-color:#faf7ef"><code class="language-java"><span style="color:#880000">16</span>:<span style="color:#880000">27</span>:<span style="color:#880000">54</span>,<span style="color:#880000">134</span> INFO [io.quarkus] (main) Quarkus <span style="color:#880000">2.7</span><span style="color:#880000">.3</span>.Final on JVM started in <span style="color:#880000">2.</span>529s. Listening on: http:<span style="color:#008000">//localhost:8081</span> <span style="color:#880000">16</span>:<span style="color:#880000">27</span>:<span style="color:#880000">54</span>,<span style="color:#880000">135</span> INFO [io.quarkus] (main) Profile test activated. <span style="color:#880000">16</span>:<span style="color:#880000">27</span>:<span style="color:#880000">54</span>,<span style="color:#880000">135</span> INFO [io.quarkus] (main) Installed features: [agroal, cdi, narayana-jta, resteasy, smallrye-context-propagation, vertx] <span style="color:#880000">16</span>:<span style="color:#880000">27</span>:<span style="color:#880000">54</span>,<span style="color:#880000">147</span> INFO [com.bol.lif.Hello] (main) Hello_ClientProxy at instance <span style="color:#880000">16</span>:<span style="color:#880000">27</span>:<span style="color:#880000">54</span>,<span style="color:#880000">710</span> INFO [com.bol.<span style="color:#a31515">int</span>.imp.LifeCycleInterceptor] (main) start AroundConstruct <span style="color:#880000">16</span>:<span style="color:#880000">27</span>:<span style="color:#880000">54</span>,<span style="color:#880000">711</span> INFO [com.bol.lif.Hello] (main) Hello_Subclass at instance <span style="color:#880000">16</span>:<span style="color:#880000">27</span>:<span style="color:#880000">54</span>,<span style="color:#880000">711</span> INFO [com.bol.<span style="color:#a31515">int</span>.imp.LifeCycleInterceptor] (main) end AroundConstruct <span style="color:#880000">16</span>:<span style="color:#880000">27</span>:<span style="color:#880000">54</span>,<span style="color:#880000">711</span> INFO [com.bol.<span style="color:#a31515">int</span>.imp.LifeCycleInterceptor] (main) life cycle PostConstruct <span style="color:#880000">16</span>:<span style="color:#880000">27</span>:<span style="color:#880000">54</span>,<span style="color:#880000">712</span> INFO [com.bol.lif.Hello] (main) at doPostConstruct <span style="color:#880000">16</span>:<span style="color:#880000">27</span>:<span style="color:#880000">54</span>,<span style="color:#880000">712</span> INFO [com.bol.lif.Hello] (main) Hello world! <span style="color:#880000">16</span>:<span style="color:#880000">27</span>:<span style="color:#880000">54</span>,<span style="color:#880000">747</span> INFO [com.bol.<span style="color:#a31515">int</span>.imp.LifeCycleInterceptor] (main) life cycle PreDestroy <span style="color:#880000">16</span>:<span style="color:#880000">27</span>:<span style="color:#880000">54</span>,<span style="color:#880000">747</span> INFO [com.bol.lif.Hello] (main) at PreDestroy <span style="color:#880000">16</span>:<span style="color:#880000">27</span>:<span style="color:#880000">54</span>,<span style="color:#880000">765</span> INFO [io.quarkus] (main) Quarkus stopped in <span style="color:#880000">0.</span>044s </code></span></span>
试想这样的场景：我的bean在销毁前要做自定义操作，但是如果用之前的两种方案，可能面临以下问题：
不适合修改bean的代码，bean的类可能是第三方库
也不适合修改生命周期拦截器代码，拦截器可能也是第三方库，也可能是多个bean共用，若修改会影响其他bean
好在quarkus为我们提供了另一个方案，不用修改bean和拦截器的代码，用注解dispose修饰指定方法即可，接下来编码验证
增加一个普通类ResourceManager.java，假设这是业务中的资源管理服务，可以打开和关闭业务资源，稍后会在配置类中将其指定为bean
<span style="color:#393939"><span style="background-color:#faf7ef"><code class="language-java"><span style="color:#0000ff">package</span> com.bolingcavalry.service.impl;
<span style="color:#0000ff">import</span> io.quarkus.logging.Log;
<span style="color:#008000">/**
* <span style="color:#808080">@author</span> zq2599@gmail.com
* <span style="color:#808080">@Title</span>: 资源管理类
* <span style="color:#808080">@Package</span>
* <span style="color:#808080">@Description</span>:
* <span style="color:#808080">@date</span> 4/10/22 10:20 AM
*/</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">class</span> <span style="color:#a31515">ResourceManager</span> {
<span style="color:#0000ff">public</span> <span style="color:#a31515">ResourceManager</span> () {
Log.info(<span style="color:#a31515">"create instance, "</span> + <span style="color:#0000ff">this</span>.getClass().getSimpleName());
}
<span style="color:#008000">/**
* 假设再次方法中打开资源，如网络、文件、数据库等
*/</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span> <span style="color:#a31515">open</span>() {
Log.info(<span style="color:#a31515">"open resource here"</span>);
}
<span style="color:#008000">/**
* 假设在此方法中关闭所有已打开的资源
*/</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span> <span style="color:#a31515">closeAll</span>() {
Log.info(<span style="color:#a31515">"close all resource here"</span>);
}
}
</code></span></span>配置类SelectBeanConfiguration.java，指定了ResourceManager的生命周期是每次http请求
<span style="color:#393939"><span style="background-color:#faf7ef"><code class="language-java"><span style="color:#0000ff">package</span> com.bolingcavalry.config;
<span style="color:#0000ff">import</span> com.bolingcavalry.service.impl.ResourceManager;
<span style="color:#0000ff">import</span> javax.enterprise.context.RequestScoped;
<span style="color:#0000ff">public</span> <span style="color:#0000ff">class</span> <span style="color:#a31515">SelectBeanConfiguration</span> {
<span style="color:#2b91af">@RequestScoped</span>
<span style="color:#0000ff">public</span> ResourceManager <span style="color:#a31515">getResourceManager</span>() {
<span style="color:#0000ff">return</span> <span style="color:#0000ff">new</span> <span style="color:#a31515">ResourceManager</span>();
}
}
</code></span></span>再写一个web服务类ResourceManagerController.java，这里面使用了ResourceManager
<span style="color:#393939"><span style="background-color:#faf7ef"><code class="language-java"><span style="color:#0000ff">package</span> com.bolingcavalry;
<span style="color:#0000ff">import</span> com.bolingcavalry.service.impl.ResourceManager;
<span style="color:#0000ff">import</span> javax.inject.Inject;
<span style="color:#0000ff">import</span> javax.ws.rs.GET;
<span style="color:#0000ff">import</span> javax.ws.rs.Path;
<span style="color:#0000ff">import</span> javax.ws.rs.Produces;
<span style="color:#0000ff">import</span> javax.ws.rs.core.MediaType;
<span style="color:#2b91af">@Path("/resourcemanager")</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">class</span> <span style="color:#a31515">ResourceManagerController</span> {
<span style="color:#2b91af">@Inject</span>
ResourceManager resourceManager;
<span style="color:#2b91af">@GET</span>
<span style="color:#2b91af">@Produces(MediaType.TEXT_PLAIN)</span>
<span style="color:#0000ff">public</span> String <span style="color:#a31515">get</span>() {
resourceManager.open();
<span style="color:#0000ff">return</span> <span style="color:#a31515">"success"</span>;
}
}
</code></span></span>由于ResourceManager的生命周期是RequestScoped，因此每次请求/resourcemanager都会实例化一个ResourceManager，请求结束后再将其销毁
现在，业务需求是每个ResourceManager的bean在销毁前，都要求其closeAll方法被执行
重点来了，在SelectBeanConfiguration.java中新增一个方法，入参是bean，而且要用Disposes注解修饰，如此，ResourceManager类型的bean在销毁前此方法都会被执行
<span style="color:#393939"><span style="background-color:#faf7ef"><code class="language-java"><span style="color:#008000">/**
* 使用了Disposes注解后，ResourceManager类型的bean在销毁前，此方法都会执行
* <span style="color:#808080">@param</span> resourceManager
*/</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span> <span style="color:#a31515">closeResource</span>(<span style="color:#2b91af">@Disposes</span> ResourceManager resourceManager) {
<span style="color:#008000">// 在这里可以做一些额外的操作，不需要bean参与</span>
Log.info(<span style="color:#a31515">"do other things that bean do not care"</span>);
<span style="color:#008000">// 也可以执行bean的方法</span>
resourceManager.closeAll();
}
</code></span></span>最后是单元测试类DisposeTest.java，这里用了注解RepeatedTest表示重复执行，属性值为3，表示重复执行3次
<span style="color:#393939"><span style="background-color:#faf7ef"><code class="language-java"><span style="color:#2b91af">@QuarkusTest</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">class</span> <span style="color:#a31515">DisposeTest</span> {
<span style="color:#2b91af">@RepeatedTest(3)</span>
<span style="color:#0000ff">public</span> <span style="color:#0000ff">void</span> <span style="color:#a31515">test</span>() {
given()
.when().get(<span style="color:#a31515">"/resourcemanager"</span>)
.then()
.statusCode(<span style="color:#880000">200</span>)
<span style="color:#008000">// 检查body内容</span>
.body(is(<span style="color:#a31515">"success"</span>));
}
}
</code></span></span>执行单元测试，控制台输出如下图，可见每次请求都有bean创建，也伴随着bean销毁，每次销毁都会执行closeResource方法，符合预期
至此，生命周期回调相关的实战就完成了，希望能给您一些参考，接下来的文章会继续深入学习依赖注入相关的知识点