Servlet容器有兩個(gè)主要的模塊，即連接器(connector)與容器(container)，本文接下來創(chuàng)建一個(gè)連接器來增強(qiáng)前面文章中的應(yīng)用程序的功能，以一種更優(yōu)雅的方式來創(chuàng)建request對(duì)象和response對(duì)象;為了兼容Servlet 2.3和2.4，連接器這里創(chuàng)建的是javax.servlet.http.HttpServletRequest對(duì)象和javax.servlet.http.HttpServletResponse對(duì)象（servlet對(duì)象類型可以是實(shí)現(xiàn)javax.servlet.Servlet接口或繼承自javax.servlet.GenericServlet類或javax.servlet.http.HttpServlet類）。
在本文的應(yīng)用程序中，連接器會(huì)解析http請(qǐng)求頭、cookies和請(qǐng)求參數(shù)等；同時(shí)修改了Response類的getWriter()方法，使其工作得更好。
本文首先要介紹一下在servlet容器中是怎么實(shí)現(xiàn)錯(cuò)誤消息國際化的，這里主要是StringManager類實(shí)現(xiàn)的功能
Tomcat是將錯(cuò)誤消息存儲(chǔ)在properties文件中，便于讀取和編輯；可是由于 tomcat的類特別多，將所有類使用的錯(cuò)誤消息都存儲(chǔ)在同一個(gè)properties文件中將會(huì)造成維護(hù)的困難；所以tomcat的處理方式是將properties劃分在不同的包中，每個(gè)properties文件都是用StringManager類的一個(gè)實(shí)例來處理，這樣在tomcat運(yùn)行時(shí)，會(huì)產(chǎn)生StringManager類的多個(gè)實(shí)例；同一個(gè)包里面的類共享一個(gè)StringManager類的實(shí)例（這里采用單例模式）；這些不同包用到的的StringManager類的實(shí)例存儲(chǔ)在一個(gè)hashtable容器中，以包名作為key存儲(chǔ)StringManager類的實(shí)例
public
class
StringManager {
/**
* The ResourceBundle for this StringManager.
*/
private
ResourceBundle bundle;
/**
* Creates a new StringManager for a given package. This is a
* private method and all access to it is arbitrated by the
* static getManager method call so that only one StringManager
* per package will be created.
*
*
@param
packageName Name of package to create StringManager for.
*/
private
StringManager(String packageName) {
String bundleName
= packageName + ".LocalStrings"
;
bundle
=
ResourceBundle.getBundle(bundleName);
}
/**
* Get a string from the underlying resource bundle.
*
*
@param
key
*/
public
String getString(String key) {
if
(key ==
null
) {
String msg
= "key is null"
;
throw
new
NullPointerException(msg);
}
String str
=
null
;
try
{
str
=
bundle.getString(key);
}
catch
(MissingResourceException mre) {
str
= "Cannot find message associated with key '" + key + "'"
;
}
return
str;
}
//
--------------------------------------------------------------
//
STATIC SUPPORT METHODS
//
--------------------------------------------------------------
private
static
Hashtable managers =
new
Hashtable();
/**
* Get the StringManager for a particular package. If a manager for
* a package already exists, it will be reused, else a new
* StringManager will be created and returned.
*
*
@param
packageName
*/
public
synchronized
static
StringManager getManager(String packageName) {
StringManager mgr
=
(StringManager)managers.get(packageName);
if
(mgr ==
null
) {
mgr
=
new
StringManager(packageName);
managers.put(packageName, mgr);
}
return
mgr;
}
}
下面我們來分析連接器是怎樣實(shí)現(xiàn)的：
public
class
HttpConnector
implements
Runnable {
boolean
stopped;
private
String scheme = "http"
;
public
String getScheme() {
return
scheme;
}
public
void
run() {
ServerSocket serverSocket
=
null
;
int
port = 8080
;
try
{
serverSocket
=
new
ServerSocket(port, 1, InetAddress.getByName("127.0.0.1"
));
}
catch
(IOException e) {
e.printStackTrace();
System.exit(
1
);
}
while
(!
stopped) {
//
Accept the next incoming connection from the server socket
Socket socket =
null
;
try
{
socket
=
serverSocket.accept();
}
catch
(Exception e) {
continue
;
}
//
Hand this socket off to an HttpProcessor
HttpProcessor processor =
new
HttpProcessor(
this
);
processor.process(socket);
}
}
public
void
start() {
Thread thread
=
new
Thread(
this
);
thread.start();
}
}
我們從HttpConnector連接器的實(shí)現(xiàn)可以看到，該連接器負(fù)責(zé)監(jiān)聽客戶端請(qǐng)求，當(dāng)監(jiān)聽到客戶端請(qǐng)求時(shí)，將獲取的socket對(duì)象交給HttpProcessor對(duì)象的process()方法處理
我們接下來分析HttpProcessor類的實(shí)現(xiàn)：
/*
this class used to be called HttpServer
*/
public
class
HttpProcessor {
public
HttpProcessor(HttpConnector connector) {
this
.connector =
connector;
}
/**
* The HttpConnector with which this processor is associated.
*/
private
HttpConnector connector =
null
;
private
HttpRequest request;
private
HttpResponse response;
public
void
process(Socket socket) {
SocketInputStream input
=
null
;
OutputStream output
=
null
;
try
{
//
包裝為SocketInputStream對(duì)象
input
=
new
SocketInputStream(socket.getInputStream(), 2048
);
output
=
socket.getOutputStream();
//
create HttpRequest object and parse
request =
new
HttpRequest(input);
//
create HttpResponse object
response =
new
HttpResponse(output);
response.setRequest(request);
response.setHeader(
"Server", "Pyrmont Servlet Container"
);
//
解析請(qǐng)求行
parseRequest(input, output);
//
解析請(qǐng)求頭
parseHeaders(input);
//
check if this is a request for a servlet or a static resource
//
a request for a servlet begins with "/servlet/"
if
(request.getRequestURI().startsWith("/servlet/"
)) {
ServletProcessor processor
=
new
ServletProcessor();
processor.process(request, response);
}
else
{
StaticResourceProcessor processor
=
new
StaticResourceProcessor();
processor.process(request, response);
}
//
Close the socket
socket.close();
//
no shutdown for this application
}
catch
(Exception e) {
e.printStackTrace();
}
}
上面的方法中獲取socket對(duì)象的輸入流與輸出流分別創(chuàng)建Request對(duì)象與Response對(duì)象，然后解析http請(qǐng)求行與請(qǐng)求頭（并填充到Request對(duì)象的相應(yīng)屬性），最后分發(fā)給處理器處理
接下來的Request對(duì)象實(shí)現(xiàn)了javax.servlet.http.HttpServletRequest接口，主要是提供一些設(shè)置相關(guān)請(qǐng)求參數(shù)的方法和獲取相關(guān)請(qǐng)求參數(shù)的方法
http請(qǐng)求頭、cookies和請(qǐng)求參數(shù)等信息分別存儲(chǔ)在如下成員變量中
protected ArrayList cookies = new ArrayList();
protected HashMap headers = new HashMap();
protected ParameterMap parameters = null;
需要注意的是protected void parseParameters()方法只需執(zhí)行一次，該方法是用來初始化ParameterMap parameters成員變量，方法如下
/**
* Parse the parameters of this request, if it has not already occurred.
* If parameters are present in both the query string and the request
* content, they are merged.
*/
protected
void
parseParameters() {
if
(parsed)
return
;
ParameterMap results
=
parameters;
if
(results ==
null
)
results
=
new
ParameterMap();
results.setLocked(
false
);
String encoding
=
getCharacterEncoding();
if
(encoding ==
null
)
encoding
= "ISO-8859-1"
;
//
Parse any parameters specified in the query string
String queryString =
getQueryString();
try
{
RequestUtil.parseParameters(results, queryString, encoding);
}
catch
(UnsupportedEncodingException e) {
;
}
//
Parse any parameters specified in the input stream
String contentType =
getContentType();
if
(contentType ==
null
)
contentType
= ""
;
int
semicolon = contentType.indexOf(';'
);
if
(semicolon >= 0
) {
contentType
= contentType.substring(0
, semicolon).trim();
}
else
{
contentType
=
contentType.trim();
}
if
("POST".equals(getMethod()) && (getContentLength() > 0
)
&& "application/x-www-form-urlencoded"
.equals(contentType)) {
try
{
int
max =
getContentLength();
int
len = 0
;
byte
buf[] =
new
byte
[getContentLength()];
ServletInputStream is
=
getInputStream();
while
(len <
max) {
int
next = is.read(buf, len, max -
len);
if
(next < 0
) {
break
;
}
len
+=
next;
}
is.close();
if
(len <
max) {
throw
new
RuntimeException("Content length mismatch"
);
}
RequestUtil.parseParameters(results, buf, encoding);
}
catch
(UnsupportedEncodingException ue) {
;
}
catch
(IOException e) {
throw
new
RuntimeException("Content read fail"
);
}
}
//
Store the final results
results.setLocked(
true
);
parsed
=
true
;
parameters
=
results;
}
我就不明白，該方法為什么不采取同步鎖關(guān)鍵字？難道是對(duì)初始化ParameterMap parameters成員變量次數(shù)沒有硬性要求？
上面方法中的ParameterMap對(duì)象，繼承自HashMap，采用boolean locked = false成員變量設(shè)置寫入的鎖（這玩意也有問題）
public
final
class
ParameterMap
extends
HashMap {
//
----------------------------------------------------------- Constructors
/**
* Construct a new, empty map with the default initial capacity and
* load factor.
*/
public
ParameterMap() {
super
();
}
/**
* Construct a new, empty map with the specified initial capacity and
* default load factor.
*
*
@param
initialCapacity The initial capacity of this map
*/
public
ParameterMap(
int
initialCapacity) {
super
(initialCapacity);
}
/**
* Construct a new, empty map with the specified initial capacity and
* load factor.
*
*
@param
initialCapacity The initial capacity of this map
*
@param
loadFactor The load factor of this map
*/
public
ParameterMap(
int
initialCapacity,
float
loadFactor) {
super
(initialCapacity, loadFactor);
}
/**
* Construct a new map with the same mappings as the given map.
*
*
@param
map Map whose contents are dupliated in the new map
*/
public
ParameterMap(Map map) {
super
(map);
}
//
------------------------------------------------------------- Properties
/**
* The current lock state of this parameter map.
*/
private
boolean
locked =
false
;
/**
* Return the locked state of this parameter map.
*/
public
boolean
isLocked() {
return
(
this
.locked);
}
/**
* Set the locked state of this parameter map.
*
*
@param
locked The new locked state
*/
public
void
setLocked(
boolean
locked) {
this
.locked =
locked;
}
/**
* The string manager for this package.
*/
private
static
final
StringManager sm =
StringManager.getManager(
"org.apache.catalina.util"
);
//
--------------------------------------------------------- Public Methods
/**
* Remove all mappings from this map.
*
*
@exception
IllegalStateException if this map is currently locked
*/
public
void
clear() {
if
(locked)
throw
new
IllegalStateException
(sm.getString(
"parameterMap.locked"
));
super
.clear();
}
/**
* Associate the specified value with the specified key in this map. If
* the map previously contained a mapping for this key, the old value is
* replaced.
*
*
@param
key Key with which the specified value is to be associated
*
@param
value Value to be associated with the specified key
*
*
@return
The previous value associated with the specified key, or
* <code>null</code> if there was no mapping for key
*
*
@exception
IllegalStateException if this map is currently locked
*/
public
Object put(Object key, Object value) {
if
(locked)
throw
new
IllegalStateException
(sm.getString(
"parameterMap.locked"
));
return
(
super
.put(key, value));
}
/**
* Copy all of the mappings from the specified map to this one. These
* mappings replace any mappings that this map had for any of the keys
* currently in the specified Map.
*
*
@param
map Mappings to be stored into this map
*
*
@exception
IllegalStateException if this map is currently locked
*/
public
void
putAll(Map map) {
if
(locked)
throw
new
IllegalStateException
(sm.getString(
"parameterMap.locked"
));
super
.putAll(map);
}
/**
* Remove the mapping for this key from the map if present.
*
*
@param
key Key whose mapping is to be removed from the map
*
*
@return
The previous value associated with the specified key, or
* <code>null</code> if there was no mapping for that key
*
*
@exception
IllegalStateException if this map is currently locked
*/
public
Object remove(Object key) {
if
(locked)
throw
new
IllegalStateException
(sm.getString(
"parameterMap.locked"
));
return
(
super
.remove(key));
}
}
同樣Response對(duì)象實(shí)現(xiàn)了javax.servlet.http.HttpServletResponse接口
這里改寫了前面文章中的getWriter()方法輸出字符流到客戶端
public
PrintWriter getWriter()
throws
IOException {
ResponseStream newStream
=
new
ResponseStream(
this
);
newStream.setCommit(
false
);
OutputStreamWriter osr
=
new
OutputStreamWriter(newStream, getCharacterEncoding());
writer
=
new
ResponseWriter(osr);
return
writer;
}
---------------------------------------------------------------------------?
本系列How Tomcat Works系本人原創(chuàng)?
轉(zhuǎn)載請(qǐng)注明出處 博客園 刺猬的溫馴?
本人郵箱： chenying998179 # 163.com （ #改為@ ）
更多文章、技術(shù)交流、商務(wù)合作、聯(lián)系博主
微信掃碼或搜索：z360901061
微信掃一掃加我為好友
QQ號(hào)聯(lián)系： 360901061
您的支持是博主寫作最大的動(dòng)力，如果您喜歡我的文章，感覺我的文章對(duì)您有幫助，請(qǐng)用微信掃描下面二維碼支持博主2元、5元、10元、20元等您想捐的金額吧，狠狠點(diǎn)擊下面給點(diǎn)支持吧，站長非常感激您！手機(jī)微信長按不能支付解決辦法：請(qǐng)將微信支付二維碼保存到相冊(cè)，切換到微信，然后點(diǎn)擊微信右上角掃一掃功能，選擇支付二維碼完成支付。
【本文對(duì)您有幫助就好】元
