开篇
这篇文章主要对Tomcat 解析conf/server.xml文件进行了一下流程的分析，对比server.xml的配置文件和代码部分能够建立起一定的关联即可。
建议有兴趣研究的可以对照代码和server.xml配置文件，这样能够更好的理解。
配置解析流程
配置解析的整体步骤在我看来是按照3步骤进行的，分别如下：
- 1、创建Digester对象，调用createStartDigester方法。
- 2、加载配置文件conf/server.xml，调用configFile方法。
- 3、通过Digester解析conf/server.xml，调用digester.parse(inputSource)方法。
- 4、解析conf/server.xml前把Catalina对象push进Digester的栈顶，重要！！！
public class Catalina {
public void load() {
// 省略相关代码
// step 1 创建Digester对象
Digester digester = createStartDigester();
InputSource inputSource = null;
InputStream inputStream = null;
File file = null;
try {
try {
// step 2 加载配置文件conf/server.xml
file = configFile();
inputStream = new FileInputStream(file);
inputSource = new InputSource(file.toURI().toURL().toString());
} catch (Exception e) {
if (log.isDebugEnabled()) {
log.debug(sm.getString("catalina.configFail", file), e);
}
}
// 省略相关代码
try {
// step 2 将Catalina进行push到digester的栈顶，并开始解析conf/server.xml
inputSource.setByteStream(inputStream);
digester.push(this);
digester.parse(inputSource);
} catch (SAXParseException spe) {
log.warn("Catalina.start using " + getConfigFile() + ": " +
spe.getMessage());
return;
} catch (Exception e) {
log.warn("Catalina.start using " + getConfigFile() + ": " , e);
return;
}
} finally {
if (inputStream != null) {
try {
inputStream.close();
} catch (IOException e) {
// Ignore
}
}
}
getServer().setCatalina(this);
getServer().setCatalinaHome(Bootstrap.getCatalinaHomeFile());
getServer().setCatalinaBase(Bootstrap.getCatalinaBaseFile());
// Stream redirection
initStreams();
// Start the new server
try {
getServer().init();
} catch (LifecycleException e) {
// 省略相关代码
}
}
}
配置解析-Digester部分
Catalina的Digester的解析部分主要依据server.xml各元素的构建Digester的解析规则，规则分为三类如下：
- addObjectCreate：遇到标签后创建对象并压入栈顶。
- addSetProperties：遇到标签后设置栈顶元素对象的属性。
- addSetNext：遇到标签后将栈顶元素（child）注入到栈顶下一个元素（parent）。
public class Catalina {
protected Digester createStartDigester() {
long t1=System.currentTimeMillis();
// Initialize the digester
Digester digester = new Digester();
digester.setValidating(false);
digester.setRulesValidation(true);
HashMap<Class<?>, List<String>> fakeAttributes = new HashMap<>();
ArrayList<String> attrs = new ArrayList<>();
attrs.add("className");
fakeAttributes.put(Object.class, attrs);
digester.setFakeAttributes(fakeAttributes);
digester.setUseContextClassLoader(true);
// Configure the actions we will be using
digester.addObjectCreate("Server",
"org.apache.catalina.core.StandardServer",
"className");
digester.addSetProperties("Server");
digester.addSetNext("Server",
"setServer",
"org.apache.catalina.Server");
digester.addObjectCreate("Server/GlobalNamingResources",
"org.apache.catalina.deploy.NamingResourcesImpl");
digester.addSetProperties("Server/GlobalNamingResources");
digester.addSetNext("Server/GlobalNamingResources",
"setGlobalNamingResources",
"org.apache.catalina.deploy.NamingResourcesImpl");
digester.addObjectCreate("Server/Listener",
null, // MUST be specified in the element
"className");
digester.addSetProperties("Server/Listener");
digester.addSetNext("Server/Listener",
"addLifecycleListener",
"org.apache.catalina.LifecycleListener");
digester.addObjectCreate("Server/Service",
"org.apache.catalina.core.StandardService",
"className");
digester.addSetProperties("Server/Service");
digester.addSetNext("Server/Service",
"addService",
"org.apache.catalina.Service");
digester.addObjectCreate("Server/Service/Listener",
null, // MUST be specified in the element
"className");
digester.addSetProperties("Server/Service/Listener");
digester.addSetNext("Server/Service/Listener",
"addLifecycleListener",
"org.apache.catalina.LifecycleListener");
//Executor
digester.addObjectCreate("Server/Service/Executor",
"org.apache.catalina.core.StandardThreadExecutor",
"className");
digester.addSetProperties("Server/Service/Executor");
digester.addSetNext("Server/Service/Executor",
"addExecutor",
"org.apache.catalina.Executor");
digester.addRule("Server/Service/Connector",
new ConnectorCreateRule());
digester.addRule("Server/Service/Connector",
new SetAllPropertiesRule(new String[]{"executor", "sslImplementationName"}));
digester.addSetNext("Server/Service/Connector",
"addConnector",
"org.apache.catalina.connector.Connector");
digester.addObjectCreate("Server/Service/Connector/SSLHostConfig",
"org.apache.tomcat.util.net.SSLHostConfig");
digester.addSetProperties("Server/Service/Connector/SSLHostConfig");
digester.addSetNext("Server/Service/Connector/SSLHostConfig",
"addSslHostConfig",
"org.apache.tomcat.util.net.SSLHostConfig");
digester.addRule("Server/Service/Connector/SSLHostConfig/Certificate",
new CertificateCreateRule());
digester.addRule("Server/Service/Connector/SSLHostConfig/Certificate",
new SetAllPropertiesRule(new String[]{"type"}));
digester.addSetNext("Server/Service/Connector/SSLHostConfig/Certificate",
"addCertificate",
"org.apache.tomcat.util.net.SSLHostConfigCertificate");
digester.addObjectCreate("Server/Service/Connector/SSLHostConfig/OpenSSLConf",
"org.apache.tomcat.util.net.openssl.OpenSSLConf");
digester.addSetProperties("Server/Service/Connector/SSLHostConfig/OpenSSLConf");
digester.addSetNext("Server/Service/Connector/SSLHostConfig/OpenSSLConf",
"setOpenSslConf",
"org.apache.tomcat.util.net.openssl.OpenSSLConf");
digester.addObjectCreate("Server/Service/Connector/SSLHostConfig/OpenSSLConf/OpenSSLConfCmd",
"org.apache.tomcat.util.net.openssl.OpenSSLConfCmd");
digester.addSetProperties("Server/Service/Connector/SSLHostConfig/OpenSSLConf/OpenSSLConfCmd");
digester.addSetNext("Server/Service/Connector/SSLHostConfig/OpenSSLConf/OpenSSLConfCmd",
"addCmd",
"org.apache.tomcat.util.net.openssl.OpenSSLConfCmd");
digester.addObjectCreate("Server/Service/Connector/Listener",
null, // MUST be specified in the element
"className");
digester.addSetProperties("Server/Service/Connector/Listener");
digester.addSetNext("Server/Service/Connector/Listener",
"addLifecycleListener",
"org.apache.catalina.LifecycleListener");
digester.addObjectCreate("Server/Service/Connector/UpgradeProtocol",
null, // MUST be specified in the element
"className");
digester.addSetProperties("Server/Service/Connector/UpgradeProtocol");
digester.addSetNext("Server/Service/Connector/UpgradeProtocol",
"addUpgradeProtocol",
"org.apache.coyote.UpgradeProtocol");
// Add RuleSets for nested elements
digester.addRuleSet(new NamingRuleSet("Server/GlobalNamingResources/"));
digester.addRuleSet(new EngineRuleSet("Server/Service/"));
digester.addRuleSet(new HostRuleSet("Server/Service/Engine/"));
digester.addRuleSet(new ContextRuleSet("Server/Service/Engine/Host/"));
addClusterRuleSet(digester, "Server/Service/Engine/Host/Cluster/");
digester.addRuleSet(new NamingRuleSet("Server/Service/Engine/Host/Context/"));
// When the 'engine' is found, set the parentClassLoader.
digester.addRule("Server/Service/Engine",
new SetParentClassLoaderRule(parentClassLoader));
addClusterRuleSet(digester, "Server/Service/Engine/Cluster/");
long t2=System.currentTimeMillis();
if (log.isDebugEnabled()) {
log.debug("Digester for server.xml created " + ( t2-t1 ));
}
return (digester);
}
}
server.xml配置文件
贴出server.xml便于对比进行理解。
<?xml version="1.0" encoding="UTF-8"?>
<!--
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<!-- Note: A "Server" is not itself a "Container", so you may not
define subcomponents such as "Valves" at this level.
Documentation at /docs/config/server.html
-->
<Server port="8005" shutdown="SHUTDOWN">
<Listener className="org.apache.catalina.startup.VersionLoggerListener" />
<!-- Security listener. Documentation at /docs/config/listeners.html
<Listener className="org.apache.catalina.security.SecurityListener" />
-->
<!--APR library loader. Documentation at /docs/apr.html -->
<Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="on" />
<!-- Prevent memory leaks due to use of particular java/javax APIs-->
<Listener className="org.apache.catalina.core.JreMemoryLeakPreventionListener" />
<Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" />
<Listener className="org.apache.catalina.core.ThreadLocalLeakPreventionListener" />
<!-- Global JNDI resources
Documentation at /docs/jndi-resources-howto.html
-->
<GlobalNamingResources>
<!-- Editable user database that can also be used by
UserDatabaseRealm to authenticate users
-->
<Resource name="UserDatabase" auth="Container"
type="org.apache.catalina.UserDatabase"
description="User database that can be updated and saved"
factory="org.apache.catalina.users.MemoryUserDatabaseFactory"
pathname="conf/tomcat-users.xml" />
</GlobalNamingResources>
<!-- A "Service" is a collection of one or more "Connectors" that share
a single "Container" Note: A "Service" is not itself a "Container",
so you may not define subcomponents such as "Valves" at this level.
Documentation at /docs/config/service.html
-->
<Service name="Catalina">
<!--The connectors can use a shared executor, you can define one or more named thread pools-->
<!--
<Executor name="tomcatThreadPool" namePrefix="catalina-exec-"
maxThreads="150" minSpareThreads="4"/>
-->
<!-- A "Connector" represents an endpoint by which requests are received
and responses are returned. Documentation at :
Java HTTP Connector: /docs/config/http.html
Java AJP Connector: /docs/config/ajp.html
APR (HTTP/AJP) Connector: /docs/apr.html
Define a non-SSL/TLS HTTP/1.1 Connector on port 8080
-->
<Connector port="8080" protocol="HTTP/1.1"
connectionTimeout="20000"
redirectPort="8443" />
<!-- A "Connector" using the shared thread pool-->
<!--
<Connector executor="tomcatThreadPool"
port="8080" protocol="HTTP/1.1"
connectionTimeout="20000"
redirectPort="8443" />
-->
<!-- Define a SSL/TLS HTTP/1.1 Connector on port 8443
This connector uses the NIO implementation. The default
SSLImplementation will depend on the presence of the APR/native
library and the useOpenSSL attribute of the
AprLifecycleListener.
Either JSSE or OpenSSL style configuration may be used regardless of
the SSLImplementation selected. JSSE style configuration is used below.
-->
<!--
<Connector port="8443" protocol="org.apache.coyote.http11.Http11NioProtocol"
maxThreads="150" SSLEnabled="true">
<SSLHostConfig>
<Certificate certificateKeystoreFile="conf/localhost-rsa.jks"
type="RSA" />
</SSLHostConfig>
</Connector>
-->
<!-- Define a SSL/TLS HTTP/1.1 Connector on port 8443 with HTTP/2
This connector uses the APR/native implementation which always uses
OpenSSL for TLS.
Either JSSE or OpenSSL style configuration may be used. OpenSSL style
configuration is used below.
-->
<!--
<Connector port="8443" protocol="org.apache.coyote.http11.Http11AprProtocol"
maxThreads="150" SSLEnabled="true" >
<UpgradeProtocol className="org.apache.coyote.http2.Http2Protocol" />
<SSLHostConfig>
<Certificate certificateKeyFile="conf/localhost-rsa-key.pem"
certificateFile="conf/localhost-rsa-cert.pem"
certificateChainFile="conf/localhost-rsa-chain.pem"
type="RSA" />
</SSLHostConfig>
</Connector>
-->
<!-- Define an AJP 1.3 Connector on port 8009 -->
<Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />
<!-- An Engine represents the entry point (within Catalina) that processes
every request. The Engine implementation for Tomcat stand alone
analyzes the HTTP headers included with the request, and passes them
on to the appropriate Host (virtual host).
Documentation at /docs/config/engine.html -->
<!-- You should set jvmRoute to support load-balancing via AJP ie :
<Engine name="Catalina" defaultHost="localhost" jvmRoute="jvm1">
-->
<Engine name="Catalina" defaultHost="localhost">
<!--For clustering, please take a look at documentation at:
/docs/cluster-howto.html (simple how to)
/docs/config/cluster.html (reference documentation) -->
<!--
<Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/>
-->
<!-- Use the LockOutRealm to prevent attempts to guess user passwords
via a brute-force attack -->
<Realm className="org.apache.catalina.realm.LockOutRealm">
<!-- This Realm uses the UserDatabase configured in the global JNDI
resources under the key "UserDatabase". Any edits
that are performed against this UserDatabase are immediately
available for use by the Realm. -->
<Realm className="org.apache.catalina.realm.UserDatabaseRealm"
resourceName="UserDatabase"/>
</Realm>
<Host name="localhost" appBase="webapps"
unpackWARs="true" autoDeploy="true">
<!-- SingleSignOn valve, share authentication between web applications
Documentation at: /docs/config/valve.html -->
<!--
<Valve className="org.apache.catalina.authenticator.SingleSignOn" />
-->
<!-- Access log processes all example.
Documentation at: /docs/config/valve.html
Note: The pattern used is equivalent to using pattern="common" -->
<Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs"
prefix="localhost_access_log" suffix=".txt"
pattern="%h %l %u %t "%r" %s %b" />
</Host>
</Engine>
</Service>
</Server>
配置解析-Digester规则构建
不管是addObjectCreate或addSetProperties或addSetNext方法，内部统一调用addRule进行规则的添加维护，这里稍微深入理解addRule方法：
- add方法判断pattern指定的模式是否存在cache(Map对象)当中
- 如果存在那么就添加pattern对应的Rule列表当中
- 如果不存在就新建pattern的list并添加Rule到列表当中
public void addObjectCreate(String pattern, String className, String attributeName) {
addRule(pattern, new ObjectCreateRule(className, attributeName));
}
public void addSetProperties(String pattern) {
addRule(pattern, new SetPropertiesRule());
}
public void addSetNext(String pattern, String methodName, String paramType) {
addRule(pattern, new SetNextRule(methodName, paramType));
}
public void addRule(String pattern, Rule rule) {
rule.setDigester(this);
getRules().add(pattern, rule);
}
public void add(String pattern, Rule rule) {
// to help users who accidentally add '/' to the end of their patterns
int patternLength = pattern.length();
if (patternLength>1 && pattern.endsWith("/")) {
pattern = pattern.substring(0, patternLength-1);
}
List<Rule> list = cache.get(pattern);
if (list == null) {
list = new ArrayList<>();
cache.put(pattern, list);
}
list.add(rule);
rules.add(rule);
if (this.digester != null) {
rule.setDigester(this.digester);
}
if (this.namespaceURI != null) {
rule.setNamespaceURI(this.namespaceURI);
}
}
Digester - Rule抽象类
Rule抽象类有核心的几个公共方法，如下：
- begin：遇到标签开头执行的方法
- end：遇到标签结束执行的方法
- finish：遇到标签全部解析完成后的方法
public abstract class Rule {
public Rule() {}
// 省略了相关的代码
// --------------------------------------------------------- Public Methods
/**
* This method is called when the beginning of a matching XML element
* is encountered. The default implementation is a NO-OP.
*
* @param namespace the namespace URI of the matching element, or an
* empty string if the parser is not namespace aware or the
* element has no namespace
* @param name the local name if the parser is namespace aware, or just
* the element name otherwise
* @param attributes The attribute list of this element
*
* @throws Exception if an error occurs while processing the event
*/
public void begin(String namespace, String name, Attributes attributes) throws Exception {
// NO-OP by default.
}
/**
* This method is called when the body of a matching XML element is
* encountered. If the element has no body, this method is not called at
* all. The default implementation is a NO-OP.
*
* @param namespace the namespace URI of the matching element, or an empty
* string if the parser is not namespace aware or the
* element has no namespace
* @param name the local name if the parser is namespace aware, or just the
* element name otherwise
* @param text The text of the body of this element
*
* @throws Exception if an error occurs while processing the event
*/
public void body(String namespace, String name, String text) throws Exception {
// NO-OP by default.
}
/**
* This method is called when the end of a matching XML element
* is encountered. The default implementation is a NO-OP.
*
* @param namespace the namespace URI of the matching element, or an empty
* string if the parser is not namespace aware or the
* element has no namespace
* @param name the local name if the parser is namespace aware, or just the
* element name otherwise
*
* @throws Exception if an error occurs while processing the event
*/
public void end(String namespace, String name) throws Exception {
// NO-OP by default.
}
/**
* This method is called after all parsing methods have been
* called, to allow Rules to remove temporary data.
*
* @throws Exception if an error occurs while processing the event
*/
public void finish() throws Exception {
// NO-OP by default.
}
