在springboot中我们经常可以引入一些starter包来集成一些工具的使用,比如spring-boot-starter-data-redis。
使用起来很方便,那么是如何实现的呢?
代码分析
我们先看注解@springbootapplication,它里面包含一个@enableautoconfiguration
继续看@enableautoconfiguration注解
@import({autoconfigurationimportselector.class})
在这个类(autoconfigurationimportselector)里面实现了自动配置的加载
主要代码片段:
string[] selectimports(annotationmetadata annotationmetadata)方法中
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autoconfigurationimportselector.autoconfigurationentry autoconfigurationentry = this.getautoconfigurationentry(autoconfigurationmetadata, annotationmetadata);
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getautoconfigurationentry方法中:
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list<string> configurations = this.getcandidateconfigurations(annotationmetadata, attributes);
protected list<string> getcandidateconfigurations(annotationmetadata metadata, annotationattributes attributes) {
list<string> configurations = springfactoriesloader.loadfactorynames(this.getspringfactoriesloaderfactoryclass(), this.getbeanclassloader());
assert.notempty(configurations, "no auto configuration classes found in meta-inf/spring.factories. if you are using a custom packaging, make sure that file is correct.");
return configurations;
}
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最后会通过springfactoriesloader.loadspringfactories去加载meta-inf/spring.factories
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enumeration<url> urls = classloader != null ? classloader.getresources("meta-inf/spring.factories") : classloader.getsystemresources("meta-inf/spring.factories");
linkedmultivaluemap result = new linkedmultivaluemap();
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while(urls.hasmoreelements()) {
url url = (url)urls.nextelement();
urlresource resource = new urlresource(url);
properties properties = propertiesloaderutils.loadproperties(resource);
iterator var6 = properties.entryset().iterator();
while(var6.hasnext()) {
entry<?, ?> entry = (entry)var6.next();
string factoryclassname = ((string)entry.getkey()).trim();
string[] var9 = stringutils.commadelimitedlisttostringarray((string)entry.getvalue());
int var10 = var9.length;
for(int var11 = 0; var11 < var10; ++var11) {
string factoryname = var9[var11];
result.add(factoryclassname, factoryname.trim());
}
}
}
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zookeeperautoconfiguration
我们来实现一个zk的autoconfiguration
首先定义一个zookeeperautoconfiguration类
然后在meta-inf/spring.factories中加入
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org.springframework.boot.autoconfigure.enableautoconfiguration=com.fayayo.fim.zookeeper.zookeeperautoconfiguration
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接下来我们看看具体的实现:
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@configurationproperties(prefix = "fim.register")
@configuration
public class urlregistry {
private string address;
private int timeout;
private int sessiontimeout;
public string getaddress() {
if (address == null) {
address = urlparam.address;
}
return address;
}
public void setaddress(string address) {
this.address = address;
}
public int gettimeout() {
if (timeout == 0) {
timeout = urlparam.connecttimeout;
}
return timeout;
}
public void settimeout(int timeout) {
this.timeout = timeout;
}
public int getsessiontimeout() {
if (sessiontimeout == 0) {
sessiontimeout = urlparam.registrysessiontimeout;
}
return sessiontimeout;
}
public void setsessiontimeout(int sessiontimeout) {
this.sessiontimeout = sessiontimeout;
}
}
@configuration
@enableconfigurationproperties(urlregistry.class)
@slf4j
public class zookeeperautoconfiguration {
@autowired
private urlregistry url;
@bean(value = "registry")
public registry createregistry() {
try {
string address = url.getaddress();
int timeout = url.gettimeout();
int sessiontimeout = url.getsessiontimeout();
log.info("init zookeeperregistry,address[{}],sessiontimeout[{}],timeout[{}]", address, timeout, sessiontimeout);
zkclient zkclient = new zkclient(address, sessiontimeout, timeout);
return new zookeeperregistry(zkclient);
} catch (zkexception e) {
log.error("[zookeeperregistry] fail to connect zookeeper, cause: " + e.getmessage());
throw e;
}
}
}
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zookeeperregistry部分实现:
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public zookeeperregistry(zkclient zkclient) {
this.zkclient = zkclient;
log.info("zk register success!");
string parentpath = urlparam.zookeeper_registry_namespace;
try {
if (!zkclient.exists(parentpath)) {
log.info("init zookeeper registry namespace");
zkclient.createpersistent(parentpath, true);
}
//监听
zkclient.subscribechildchanges(parentpath, new izkchildlistener() {
//对父节点添加监听子节点变化。
@override
public void handlechildchange(string parentpath, list<string> currentchilds) {
log.info(string.format("[zookeeperregistry] service list change: path=%s, currentchilds=%s", parentpath, currentchilds.tostring()));
if(watchnotify!=null){
watchnotify.notify(nodechildstourls(currentchilds));
}
}
});
shutdownhook.registershutdownhook(this);
} catch (exception e) {
e.printstacktrace();
log.error("failed to subscribe zookeeper");
}
}
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具体使用
那么我们怎么使用自己写的zookeeperautoconfiguration呢
首先要在需要使用的项目中引入依赖
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<dependency>
<groupid>com.fayayo</groupid>
<artifactid>fim-registry-zookeeper</artifactid>
<version>0.0.1-snapshot</version>
</dependency>
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然后配置参数
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fim:
register:
address: 192.168.88.129:2181
timeout: 2000
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如果不配置会有默认的参数
具体使用的时候只需要在bean中注入就可以了,比如
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@autowired
private registry registry;
public list<url> getall(){
list<url>list=cache.get(key);
if(collectionutils.isempty(list)){
list=registry.discover();
cache.put(key,list);
}
return list;
}
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完整代码
https://github.com/lizu18xz/fim.git
总结
以上所述是小编给大家介绍的springboot 中 autoconfiguration的使用方法，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对服务器之家网站的支持！
如果你觉得本文对你有帮助，欢迎转载，烦请注明出处，谢谢！原文链接：https://www.imooc.com/article/285008