在前面的文章中，如果我們要啟動(dòng)tomcat容器，我們需要使用Bootstrap類來實(shí)例化連接器、servlet容器、Wrapper實(shí)例和其他組件，然后調(diào)用各個(gè)對(duì)象的set方法將它們關(guān)聯(lián)起來；這種配置應(yīng)用程序的方法有一個(gè)明顯的缺陷，即所有的配置都必須硬編碼。調(diào)整組件配置和屬性值都必須要重新編譯Bootstrap類。幸運(yùn)的是，Tomcat的設(shè)計(jì)者使用了一種更加優(yōu)雅的配置方式，即使用一個(gè)名為server.xml的XML文件來對(duì)應(yīng)用程序進(jìn)行配置。server.xml文件中的每個(gè)元素都會(huì)轉(zhuǎn)換為一個(gè)java對(duì)象，元素的屬性會(huì)用于設(shè)置java對(duì)象的屬性，這樣，就可以通過簡(jiǎn)單的編輯server.xml文件來修改tomcat的配置。
Tomcat使用了開源庫Digester來將xml文件中的元素轉(zhuǎn)換成java對(duì)象。
由于一個(gè)Context實(shí)例表示一個(gè)Web應(yīng)用程序，因此配置Web應(yīng)用程序是通過對(duì)已經(jīng)實(shí)例化的Context實(shí)例進(jìn)行配置完成的。用來配置Web應(yīng)用程序的XML文件的名稱是web.xml，該文件位于Web應(yīng)用程序的WEB-INF目錄下。
下面來介紹Digester庫，Digester庫是Apache軟件基金會(huì)的Jatarta項(xiàng)目下的子Commons項(xiàng)目下的一個(gè)開源項(xiàng)目，它的主頁地址是http://commons.apache.org/proper/commons-digester/
org.apache.commons.digester3.Digester類是Digester庫中的主類，該類可用于解析XML文件，對(duì)于XML文件中的每個(gè)元素，Digester對(duì)象都會(huì)檢查它是否要做事先預(yù)定義的事件，在調(diào)用Digester對(duì)象的parse()方法之前，程序員要先定義好Digester對(duì)象執(zhí)行哪些動(dòng)作。
因此，程序員要先定義好模式，然后將每個(gè)模式與一條或多條規(guī)則相關(guān)聯(lián)。
模式通常是xml文件里面元素的路徑，類似于xpath的語法路徑
規(guī)則指明了當(dāng)Digester對(duì)象遇到了某個(gè)特殊的模式時(shí)要執(zhí)行的一個(gè)或多個(gè)動(dòng)作，規(guī)則是org.apache.commons.digester3.Rule類的實(shí)例，Digester類開源包含0個(gè)或多個(gè)Rule對(duì)象，在Digester實(shí)例中，這些規(guī)則和其相關(guān)聯(lián)的模式都存儲(chǔ)在由org.apache.commons.digester3.Rules接口表示的一類存儲(chǔ)器中，每當(dāng)把一條規(guī)則添加到Digester實(shí)例中時(shí)，Rule對(duì)象都會(huì)被添加到Rules對(duì)象中。
另外，Rule類有begin()方法和end()方法，在解析xml文件時(shí)，當(dāng)Digester實(shí)例遇到匹配某個(gè)模式的元素的開始標(biāo)簽時(shí)，它會(huì)調(diào)用相應(yīng)的Rule對(duì)象的begin()方法，而當(dāng)Digester實(shí)例遇到相應(yīng)元素的結(jié)束標(biāo)簽時(shí)，它會(huì)調(diào)用Rule對(duì)象的end()方法。
在使用Digester庫時(shí)，我們需要先導(dǎo)入相關(guān)依賴jar
<
dependency
>
<
groupId
>
org.apache.commons
</
groupId
>
<
artifactId
>
commons-digester3
</
artifactId
>
<
version
>
3.2
</
version
>
<
classifier
>
with-deps
</
classifier
>
</
dependency
>
第一個(gè)示例應(yīng)用程序演示如何使用Digester庫動(dòng)態(tài)的創(chuàng)建對(duì)象，并設(shè)置相應(yīng)的屬性值。
employee1.xml文件內(nèi)容如下
<?
xml version="1.0" encoding="ISO-8859-1"
?>
<
employee
firstName
="Brian"
lastName
="May"
>
</
employee
>
我們需要根據(jù)上面的xml文件創(chuàng)建Employee對(duì)象，并設(shè)置相應(yīng)屬性，Employee類代碼如下：
public
class
Employee {
private
String firstName;
private
String lastName;
private
ArrayList offices =
new
ArrayList();
public
Employee() {
System.out.println(
"Creating Employee"
);
}
public
String getFirstName() {
return
firstName;
}
public
void
setFirstName(String firstName) {
System.out.println(
"Setting firstName : " +
firstName);
this
.firstName =
firstName;
}
public
String getLastName() {
return
lastName;
}
public
void
setLastName(String lastName) {
System.out.println(
"Setting lastName : " +
lastName);
this
.lastName =
lastName;
}
public
void
addOffice(Office office) {
System.out.println(
"Adding Office to this employee"
);
offices.add(office);
}
public
ArrayList getOffices() {
return
offices;
}
public
void
printName() {
System.out.println(
"My name is " + firstName + " " +
lastName);
}
}
現(xiàn)在寫一個(gè)測(cè)試類Test01，它使用Digester類，并為其添加創(chuàng)建Employee對(duì)象和設(shè)置其屬性的規(guī)則。
public
class
Test01 {
public
static
void
main(String[] args) {
InputStream inputStream
=
null
;
Digester digester
=
new
Digester();
//
add rules
digester.addObjectCreate("employee","ex15.pyrmont.digestertest.Employee"
);
digester.addSetProperties(
"employee"
);
digester.addCallMethod(
"employee", "printName"
);
try
{
inputStream
= Thread.currentThread().getContextClassLoader().getResourceAsStream("employee1.xml");
Employee employee =
(Employee) digester.parse(inputStream);
System.out.println(
"First name : " +
employee.getFirstName());
System.out.println(
"Last name : " +
employee.getLastName());
}
catch
(Exception e) {
e.printStackTrace();
}
finally
{
if
(inputStream !=
null
) {
try
{
inputStream.close();
}
catch
(IOException e) {
//
TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
}
第二個(gè)示例演示如何利用Digester庫創(chuàng)建兩個(gè)對(duì)象，并建立他們之間的關(guān)系
employee2.xml 文件內(nèi)容如下
<?
xml version="1.0" encoding="ISO-8859-1"
?>
<
employee
firstName
="Freddie"
lastName
="Mercury"
>
<
office
description
="Headquarters"
>
<
address
streetName
="Wellington Avenue"
streetNumber
="223"
/>
</
office
>
<
office
description
="Client site"
>
<
address
streetName
="Downing Street"
streetNumber
="10"
/>
</
office
>
</
employee
>
然后我們還需要?jiǎng)?chuàng)建Office類和Address類
Office類代碼如下：
public
class
Office {
private
Address address;
private
String description;
public
Office() {
System.out.println(
"..Creating Office"
);
}
public
String getDescription() {
return
description;
}
public
void
setDescription(String description) {
System.out.println(
"..Setting office description : " +
description);
this
.description =
description;
}
public
Address getAddress() {
return
address;
}
public
void
setAddress(Address address) {
System.out.println(
"..Setting office address : " +
address);
this
.address =
address;
}
}
Address類代碼如下：
public
class
Address {
private
String streetName;
private
String streetNumber;
public
Address() {
System.out.println(
"....Creating Address"
);
}
public
String getStreetName() {
return
streetName;
}
public
void
setStreetName(String streetName) {
System.out.println(
"....Setting streetName : " +
streetName);
this
.streetName =
streetName;
}
public
String getStreetNumber() {
return
streetNumber;
}
public
void
setStreetNumber(String streetNumber) {
System.out.println(
"....Setting streetNumber : " +
streetNumber);
this
.streetNumber =
streetNumber;
}
public
String toString() {
return
"...." + streetNumber + " " +
streetName;
}
}
下面是Test02類的定義，該類使用一個(gè)Digester對(duì)象，并為其添加規(guī)則
public
class
Test02 {
public
static
void
main(String[] args) {
InputStream inputStream =
null
;
Digester digester
=
new
Digester();
//
add rules
digester.addObjectCreate("employee"
,
"ex15.pyrmont.digestertest.Employee"
);
digester.addSetProperties(
"employee"
);
digester.addObjectCreate(
"employee/office"
,
"ex15.pyrmont.digestertest.Office"
);
digester.addSetProperties(
"employee/office"
);
digester.addSetNext(
"employee/office", "addOffice"
);
digester.addObjectCreate(
"employee/office/address"
,
"ex15.pyrmont.digestertest.Address"
);
digester.addSetProperties(
"employee/office/address"
);
digester.addSetNext(
"employee/office/address", "setAddress"
);
try
{
inputStream
=
Thread.currentThread().getContextClassLoader()
.getResourceAsStream(
"employee2.xml");
Employee employee =
(Employee) digester.parse(inputStream);
ArrayList offices
=
employee.getOffices();
Iterator iterator
=
offices.iterator();
System.out
.println(
"-------------------------------------------------"
);
while
(iterator.hasNext()) {
Office office
=
(Office) iterator.next();
Address address
=
office.getAddress();
System.out.println(office.getDescription());
System.out.println(
"Address : " +
address.getStreetNumber()
+ " " +
address.getStreetName());
System.out.println(
"--------------------------------"
);
}
}
catch
(Exception e) {
e.printStackTrace();
}
finally
{
if
(inputStream !=
null
) {
try
{
inputStream.close();
}
catch
(IOException e) {
//
TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
}
Rule類包含了一些方法，其中最重要的兩個(gè)方法是begin()方法和end()方法，當(dāng)Digester實(shí)例遇到某個(gè)XML元素的開始標(biāo)簽時(shí)，它會(huì)調(diào)用它所包含的匹配Rule對(duì)象的begin()方法，方法簽名如下：
public void begin( String namespace, String name, Attributes attributes ) throws Exception
當(dāng)Digester實(shí)例遇到某個(gè)XML元素的結(jié)束標(biāo)簽時(shí)，它會(huì)調(diào)用它所包含的匹配Rule對(duì)象的end()方法，方法簽名如下：
public void end( String namespace, String name ) throws Exception
Digester對(duì)象是如何完成這些工作的呢？當(dāng)調(diào)用Digester對(duì)象的addObjectCreate()方法、addCallMethod()方法、addSetNext()方法或其他方法時(shí)，都會(huì)間接地調(diào)用Digester類的addRule()方法；該方法將一個(gè)Rule對(duì)象和它所匹配的模式添加到Digester對(duì)象的Rules集合中。
addRule()方法實(shí)現(xiàn)如下：
public
void
addRule( String pattern, Rule rule )
{
rule.setDigester(
this
);
getRules().add( pattern, rule );
}
查看Digester類的addObjectCreate()方法的重載實(shí)現(xiàn)如下：
public
void
addObjectCreate( String pattern, String className )
{
addRule( pattern,
new
ObjectCreateRule( className ) );
}
public
void
addObjectCreate( String pattern, Class<?>
clazz )
{
addRule( pattern,
new
ObjectCreateRule( clazz ) );
}
public
void
addObjectCreate( String pattern, String className, String attributeName )
{
addRule( pattern,
new
ObjectCreateRule( className, attributeName ) );
}
public
void
addObjectCreate( String pattern, String attributeName, Class<?>
clazz )
{
addRule( pattern,
new
ObjectCreateRule( attributeName, clazz ) );
}
這四個(gè)重載方法都調(diào)用了addRule()方法，ObjectCreateRule類是Rule類的子類，該類的實(shí)例可作為addRule()方法的第二個(gè)參數(shù)使用。
下面是ObjectCreateRule類的begin()方法和end()方法的實(shí)現(xiàn)
@Override
public
void
begin( String namespace, String name, Attributes attributes )
throws
Exception
{
Class
<?> clazz =
this
.clazz;
if
( clazz ==
null
)
{
//
Identify the name of the class to instantiate
String realClassName =
className;
if
( attributeName !=
null
)
{
String value
=
attributes.getValue( attributeName );
if
( value !=
null
)
{
realClassName
=
value;
}
}
if
( getDigester().getLogger().isDebugEnabled() )
{
getDigester().getLogger().debug( format(
"[ObjectCreateRule]{%s} New '%s'"
,
getDigester().getMatch(),
realClassName ) );
}
//
Instantiate the new object and push it on the context stack
clazz =
getDigester().getClassLoader().loadClass( realClassName );
}
Object instance;
if
( constructorArgumentTypes ==
null
|| constructorArgumentTypes.length == 0
)
{
if
( getDigester().getLogger().isDebugEnabled() )
{
getDigester()
.getLogger()
.debug( format(
"[ObjectCreateRule]{%s} New '%s' using default empty constructor"
,
getDigester().getMatch(),
clazz.getName() ) );
}
instance
=
clazz.newInstance();
}
else
{
if
( proxyManager ==
null
)
{
Constructor
<?> constructor =
getAccessibleConstructor( clazz, constructorArgumentTypes );
if
( constructor ==
null
)
{
throw
new
SAXException(
format(
"[ObjectCreateRule]{%s} Class '%s' does not have a construcor with types %s"
,
getDigester().getMatch(),
clazz.getName(),
Arrays.toString( constructorArgumentTypes ) ) );
}
proxyManager
=
new
ProxyManager( clazz, constructor, defaultConstructorArguments, getDigester() );
}
instance
=
proxyManager.createProxy();
}
getDigester().push( instance );
}
/**
* {
@inheritDoc
}
*/
@Override
public
void
end( String namespace, String name )
throws
Exception
{
Object top
=
getDigester().pop();
if
( proxyManager !=
null
)
{
proxyManager.finalize( top );
}
if
( getDigester().getLogger().isDebugEnabled() )
{
getDigester().getLogger().debug( format(
"[ObjectCreateRule]{%s} Pop '%s'"
,
getDigester().getMatch(),
top.getClass().getName() ) );
}
}
begin()方法用于創(chuàng)建一個(gè)對(duì)象實(shí)例，并將其壓入到Digester對(duì)象的內(nèi)部棧中；end()方法會(huì)將內(nèi)部棧的棧頂元素彈出棧
要向Digester實(shí)例中添加Rule對(duì)象，還可以調(diào)用其addRuleSet()方法，方法實(shí)現(xiàn)如下：
public
void
addRuleSet( RuleSet ruleSet )
{
String oldNamespaceURI
=
getRuleNamespaceURI();
String newNamespaceURI
=
ruleSet.getNamespaceURI();
if
( log.isDebugEnabled() )
{
if
( newNamespaceURI ==
null
)
{
log.debug(
"addRuleSet() with no namespace URI"
);
}
else
{
log.debug(
"addRuleSet() with namespace URI " +
newNamespaceURI );
}
}
setRuleNamespaceURI( newNamespaceURI );
ruleSet.addRuleInstances(
this
);
setRuleNamespaceURI( oldNamespaceURI );
}
org.apache.commons.digester3.RuleSet接口表示Rule對(duì)象的集合，該接口定義了兩個(gè)方法，分別為addRuleInstance()和getNamespaceURI()，addRuleInstance()方法簽名如下：
public void addRuleInstance(Digester digester)
addRuleInstance()方法用于添加定義在當(dāng)前RuleSet對(duì)象中的Rule對(duì)象集合到作為該方法參數(shù)傳輸?shù)腄igester實(shí)例中
getNamespaceUR()方法返回將要應(yīng)用在所有Rule對(duì)象（在當(dāng)前Ruleset中創(chuàng)建的）的命名空間的URI，該方法簽名如下
public java.lang.String getNamespaceURI()
因此，在創(chuàng)建了Digester對(duì)象之后，可以創(chuàng)建一個(gè)RuleSet對(duì)象，并將其傳輸給Digester對(duì)象的addRuleSet()方法
為了便于使用，實(shí)現(xiàn)RuleSet接口有一個(gè)基類RuleSetBase，RuleSetBase類為抽象類，提供了getNamespaceURI()方法的實(shí)現(xiàn)，我們只需要提供addRuleInstances()方法的實(shí)現(xiàn)就可以了
下面是我們創(chuàng)建的EmployeeRuleSet類的源碼（繼承自RuleSetBase類）
public
class
EmployeeRuleSet
extends
RuleSetBase {
public
void
addRuleInstances(Digester digester) {
//
add rules
digester.addObjectCreate("employee", "ex15.pyrmont.digestertest.Employee"
);
digester.addSetProperties(
"employee"
);
digester.addObjectCreate(
"employee/office", "ex15.pyrmont.digestertest.Office"
);
digester.addSetProperties(
"employee/office"
);
digester.addSetNext(
"employee/office", "addOffice"
);
digester.addObjectCreate(
"employee/office/address"
,
"ex15.pyrmont.digestertest.Address"
);
digester.addSetProperties(
"employee/office/address"
);
digester.addSetNext(
"employee/office/address", "setAddress"
);
}
}
我們注意到，EmployeeRuleSet類中的addRuleInstances()方法的實(shí)現(xiàn)的功能類似Test02類，將相同的Rule對(duì)象添加到Digester對(duì)象中
下面是Test03的代碼，里面會(huì)創(chuàng)建EmployeeRuleSet類的實(shí)例，然后將其添加到之前創(chuàng)建的Digester對(duì)象中
public
class
Test03 {
public
static
void
main(String[] args) {
InputStream inputStream =
null
;
Digester digester
=
new
Digester();
digester.addRuleSet(
new
EmployeeRuleSet());
try
{
inputStream
= Thread.currentThread().getContextClassLoader().getResourceAsStream("employee2.xml"
);
Employee employee
=
(Employee) digester.parse(inputStream);
ArrayList offices
=
employee.getOffices();
Iterator iterator
=
offices.iterator();
System.out.println(
"-------------------------------------------------"
);
while
(iterator.hasNext()) {
Office office
=
(Office) iterator.next();
Address address
=
office.getAddress();
System.out.println(office.getDescription());
System.out.println(
"Address : " +
address.getStreetNumber()
+ " " +
address.getStreetName());
System.out.println(
"--------------------------------"
);
}
}
catch
(Exception e) {
e.printStackTrace();
}
finally
{
if
(inputStream !=
null
) {
try
{
inputStream.close();
}
catch
(IOException e) {
//
TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
}
與其他類型的容器不同，StandardContext實(shí)例必須有一個(gè)監(jiān)聽器，該監(jiān)聽器會(huì)負(fù)責(zé)配置StandardContext實(shí)例，設(shè)置成功后會(huì)將StandardContext實(shí)例的變量configued值設(shè)置為tue。
StandardContext類的標(biāo)準(zhǔn)監(jiān)聽器是org.apache.catalina.startup.ContextConfig類的實(shí)例，它會(huì)執(zhí)行很對(duì)StandardContext實(shí)例來說必不可少的任務(wù)，例如安裝驗(yàn)證器閥到StandardContext實(shí)例的管道對(duì)象中，此外還會(huì)添加許可器閥（類型為org.apache.catalina.valves.CertificateValve）到管道對(duì)象中。
但更重要的是，ContextConfig類的實(shí)例還會(huì)讀取和解析默認(rèn)的web.xml文件和應(yīng)用程序自定義的web.xml文件，并將xml元素轉(zhuǎn)換為java對(duì)象。
默認(rèn)的web.xml文件位于CATALINE_HOME目錄下的conf目錄中，其中定義并映射了很多默認(rèn)的servlet，配置了很多MIME類型文件的映射，定義了默認(rèn)的session超時(shí)時(shí)間，以及定義了歡迎文件的列表。
應(yīng)用程序的web.xml文件是應(yīng)用程序自定義的配置文件，位于應(yīng)用程序目錄下的WEB-INF目錄中。
ContextConfig實(shí)例會(huì)為每一個(gè)servlet元素創(chuàng)建StandardWrapper實(shí)例，因此，正如你在本章應(yīng)用程序中看到的，配置變簡(jiǎn)單了，你不在需要實(shí)例化Wrapper實(shí)例了
因此，我們需要在Bootstrap類中實(shí)例化一個(gè)ContextConfig類，并調(diào)用org.apache.catalina.Lifecycle接口的addLifecycleListener()方法將其添加到StandardContext對(duì)象中
LifecycleListener listener =
new
ContextConfig();
((Lifecycle) context).addLifecycleListener(listener);
在啟動(dòng)和停止StandardContext實(shí)例時(shí)，會(huì)觸發(fā)相應(yīng)事件，ContextConfig類會(huì)對(duì)兩種事件做出響應(yīng)，分別為START_EVENT 和STOP_EVENT
每當(dāng)StandardContext實(shí)例觸發(fā)事件時(shí)，會(huì)調(diào)用ContextConfig實(shí)例的lifecycleEvent()方法
public
void
lifecycleEvent(LifecycleEvent event) {
//
Identify the context we are associated with
try
{
context
=
(Context) event.getLifecycle();
if
(context
instanceof
StandardContext) {
int
contextDebug =
((StandardContext) context).getDebug();
if
(contextDebug >
this
.debug)
this
.debug =
contextDebug;
}
}
catch
(ClassCastException e) {
log(sm.getString(
"contextConfig.cce"
, event.getLifecycle()), e);
return
;
}
//
Process the event that has occurred
if
(event.getType().equals(Lifecycle.START_EVENT))
start();
else
if
(event.getType().equals(Lifecycle.STOP_EVENT))
stop();
}
在上面方法中，會(huì)繼續(xù)調(diào)用start()方法和stop()方法
private
synchronized
void
start() {
if
(debug > 0
)
log(sm.getString(
"contextConfig.start"
));
context.setConfigured(
false
);
ok
=
true
;
//
Set properties based on DefaultContext
Container container =
context.getParent();
if
( !
context.getOverride() ) {
if
( container
instanceof
Host ) {
((Host)container).importDefaultContext(context);
container
=
container.getParent();
}
if
( container
instanceof
Engine ) {
((Engine)container).importDefaultContext(context);
}
}
//
Process the default and application web.xml files
defaultConfig();
applicationConfig();
if
(ok) {
validateSecurityRoles();
}
//
Scan tag library descriptor files for additional listener classes
if
(ok) {
try
{
tldScan();
}
catch
(Exception e) {
log(e.getMessage(), e);
ok
=
false
;
}
}
//
Configure a certificates exposer valve, if required
if
(ok)
certificatesConfig();
//
Configure an authenticator if we need one
if
(ok)
authenticatorConfig();
//
Dump the contents of this pipeline if requested
if
((debug >= 1) && (context
instanceof
ContainerBase)) {
log(
"Pipline Configuration:"
);
Pipeline pipeline
=
((ContainerBase) context).getPipeline();
Valve valves[]
=
null
;
if
(pipeline !=
null
)
valves
=
pipeline.getValves();
if
(valves !=
null
) {
for
(
int
i = 0; i < valves.length; i++
) {
log(
" " +
valves[i].getInfo());
}
}
log(
"======================"
);
}
//
Make our application available if no problems were encountered
if
(ok)
context.setConfigured(
true
);
else
{
log(sm.getString(
"contextConfig.unavailable"
));
context.setConfigured(
false
);
}
}
start()方法會(huì)進(jìn)一步調(diào)用defaultConfig()方法和applicationConfig()方法
defaultConfig()方法負(fù)責(zé)讀取并解析位于%CATALINA_HOME%/conf目錄下的默認(rèn)的web.xml文件
private
void
defaultConfig() {
//
Open the default web.xml file, if it exists
File file =
new
File(Constants.DefaultWebXml);
if
(!
file.isAbsolute())
file
=
new
File(System.getProperty("catalina.base"
),
Constants.DefaultWebXml);
FileInputStream stream
=
null
;
try
{
stream
=
new
FileInputStream(file.getCanonicalPath());
stream.close();
stream
=
null
;
}
catch
(FileNotFoundException e) {
log(sm.getString(
"contextConfig.defaultMissing"
));
return
;
}
catch
(IOException e) {
log(sm.getString(
"contextConfig.defaultMissing"
), e);
return
;
}
//
Process the default web.xml file
synchronized
(webDigester) {
try
{
InputSource is
=
new
InputSource("file://" +
file.getAbsolutePath());
stream
=
new
FileInputStream(file);
is.setByteStream(stream);
webDigester.setDebug(getDebug());
if
(context
instanceof
StandardContext)
((StandardContext) context).setReplaceWelcomeFiles(
true
);
webDigester.clear();
webDigester.push(context);
webDigester.parse(is);
}
catch
(SAXParseException e) {
log(sm.getString(
"contextConfig.defaultParse"
), e);
log(sm.getString(
"contextConfig.defaultPosition"
,
"" +
e.getLineNumber(),
"" +
e.getColumnNumber()));
ok
=
false
;
}
catch
(Exception e) {
log(sm.getString(
"contextConfig.defaultParse"
), e);
ok
=
false
;
}
finally
{
try
{
if
(stream !=
null
) {
stream.close();
}
}
catch
(IOException e) {
log(sm.getString(
"contextConfig.defaultClose"
), e);
}
}
}
}
applicationConfig()方法與defaultConfig()方法類似，只不過它處理的是應(yīng)用程序自定義的部署描述符，該部署描述符位于應(yīng)用目錄下的WEB-INF目錄中
private
void
applicationConfig() {
//
Open the application web.xml file, if it exists
InputStream stream =
null
;
ServletContext servletContext
=
context.getServletContext();
if
(servletContext !=
null
)
stream
=
servletContext.getResourceAsStream
(Constants.ApplicationWebXml);
if
(stream ==
null
) {
log(sm.getString(
"contextConfig.applicationMissing"
));
return
;
}
//
Process the application web.xml file
synchronized
(webDigester) {
try
{
URL url
=
servletContext.getResource(Constants.ApplicationWebXml);
InputSource is
=
new
InputSource(url.toExternalForm());
is.setByteStream(stream);
webDigester.setDebug(getDebug());
if
(context
instanceof
StandardContext) {
((StandardContext) context).setReplaceWelcomeFiles(
true
);
}
webDigester.clear();
webDigester.push(context);
webDigester.parse(is);
}
catch
(SAXParseException e) {
log(sm.getString(
"contextConfig.applicationParse"
), e);
log(sm.getString(
"contextConfig.applicationPosition"
,
"" +
e.getLineNumber(),
"" +
e.getColumnNumber()));
ok
=
false
;
}
catch
(Exception e) {
log(sm.getString(
"contextConfig.applicationParse"
), e);
ok
=
false
;
}
finally
{
try
{
if
(stream !=
null
) {
stream.close();
}
}
catch
(IOException e) {
log(sm.getString(
"contextConfig.applicationClose"
), e);
}
}
}
}
在ContextConfig類中，使用變量webDigester來引用一個(gè)Digester類型的對(duì)象
private static Digester webDigester = createWebDigester();
該Digester對(duì)象用于解析默認(rèn)的web.xml文件和應(yīng)用程序自定義的web.xml文件，在調(diào)用createWebDigester()方法時(shí)會(huì)添加用來處理web.xml文件的規(guī)則
/**
* Create (if necessary) and return a Digester configured to process the
* web application deployment descriptor (web.xml).
*/
private
static
Digester createWebDigester() {
URL url
=
null
;
Digester webDigester
=
new
Digester();
webDigester.setValidating(
true
);
url
= ContextConfig.
class
.getResource(Constants.WebDtdResourcePath_22);
webDigester.register(Constants.WebDtdPublicId_22,
url.toString());
url
= ContextConfig.
class
.getResource(Constants.WebDtdResourcePath_23);
webDigester.register(Constants.WebDtdPublicId_23,
url.toString());
webDigester.addRuleSet(
new WebRuleSet());
return
(webDigester);
}
我們注意到，上面方法中調(diào)用了變量webDigester的addRuleSet()方法，傳入一個(gè)org.apache.catalina.startup.WebRuleSet類型的對(duì)象作為參數(shù)；WebRuleSet類是org.apache.commons.digester.RuleSetBase的子類。
下面是WebRuleSet類的addRuleInstances()方法實(shí)現(xiàn)：
public
void
addRuleInstances(Digester digester) {
digester.addRule(prefix
+ "web-app"
,
new
SetPublicIdRule(digester, "setPublicId"
));
digester.addCallMethod(prefix
+ "web-app/context-param"
,
"addParameter", 2
);
digester.addCallParam(prefix
+ "web-app/context-param/param-name", 0
);
digester.addCallParam(prefix
+ "web-app/context-param/param-value", 1
);
digester.addCallMethod(prefix
+ "web-app/display-name"
,
"setDisplayName", 0
);
digester.addRule(prefix
+ "web-app/distributable"
,
new
SetDistributableRule(digester));
digester.addObjectCreate(prefix
+ "web-app/ejb-local-ref"
,
"org.apache.catalina.deploy.ContextLocalEjb"
);
digester.addSetNext(prefix
+ "web-app/ejb-local-ref"
,
"addLocalEjb"
,
"org.apache.catalina.deploy.ContextLocalEjb"
);
//
代碼太長，后面部分略
}
---------------------------------------------------------------------------?
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