eXtremeComponents（简称ec）是一系列提供高级显示的开源JSP定制标签，当前的包含的组件为eXtremeTable，用于以表形式显示数据。
其本质是jsp的自定义标签，抓住这一点就抓住了ec的本源。
1. Table定义
我们先看一下标签的定义：extremComponents.tld，其中table的标签定义如下：
<tag>
<name>table</name>
<tag-class>org.extremecomponents.table.tag.TableTag</tag-class>
<body-content>JSP</body-content>
<display-name>TableTag</display-name>
<description><![CDATA[The container which holds all the main table information. Will also hold global information if needed. The table tag is copied into the Table and encapsulated in the Model.]]></description>
<attribute>
<name>action</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The URI that will be called when the filter, sort and pagination is used.]]></description>
</attribute>
<attribute>
<name>autoIncludeParameters</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[Specify whether or not to automatically include the parameters, as hidden inputs, passed into the JSP.]]></description>
</attribute>
<attribute>
<name>border</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The table border attribute. The default is 0.]]></description>
</attribute>
<attribute>
<name>bufferView</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[Whether of not to buffer the view. Boolean value with the default being false.]]></description>
</attribute>
<attribute>
<name>cellpadding</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The table cellpadding attribute. The default is 0.]]></description>
</attribute>
<attribute>
<name>cellspacing</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The table cellspacing attribute. The default is 0.]]></description>
</attribute>
<attribute>
<name>filterable</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[Specify whether or not the table is filterable. Boolean value with the default being true.]]></description>
</attribute>
<attribute>
<name>filterRowsCallback</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[A fully qualified class name to a custom FilterRowsCallback implementation. Could also be a named type in the preferences. Used to filter the Collection of Beans or Collection of Maps.]]></description>
</attribute>
<attribute>
<name>form</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The reference to a surrounding form element.]]></description>
</attribute>
<attribute>
<name>imagePath</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The path to find the images. For example imagePath=/extremesite/images/*.png is saying look in the image directory for the .png images.]]></description>
</attribute>
<attribute>
<name>interceptor</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[A fully qualified class name to a custom InterceptTable implementation. Could also be a named type in the preferences. Used to add table attributes.]]></description>
</attribute>
<attribute>
<name>items</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[Reference the collection that will be retrieved.]]></description>
</attribute>
<attribute>
<name>locale</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The locale for this table. For example fr_FR is used for the French translation.]]></description>
</attribute>
<attribute>
<name>method</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[Used to invoke the table action using a POST or GET.]]></description>
</attribute>
<attribute>
<name>onInvokeAction</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The javascript that will be invoked when a table action enabled.]]></description>
</attribute>
<attribute>
<name>retrieveRowsCallback</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[A fully qualified class name to a custom RetrieveRowsCallback implementation. Could also be a named type in the preferences. Used to retrieve the Collection of Beans or Collection of Maps.]]></description>
</attribute>
<attribute>
<name>rowsDisplayed</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The number of rows to display in the table.]]></description>
</attribute>
<attribute>
<name>scope</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The scope (page, request, session, or application) to find the Collection of beans or Collection of Maps defined by the collection attribute.]]></description>
</attribute>
<attribute>
<name>showPagination</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[Specify whether or not the table should use pagination. Boolean value with the default being true.]]></description>
</attribute>
<attribute>
<name>showExports</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[Specify whether or not the table should use the exports. Boolean value with the default being true.]]></description>
</attribute>
<attribute>
<name>showStatusBar</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[Specify whether or not the table should use the status bar. Boolean value with the default being true.]]></description>
</attribute>
<attribute>
<name>showTitle</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[Specify whether or not to show the title. Boolean value with the default being true.]]></description>
</attribute>
<attribute>
<name>showTooltips</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[Specify whether or not to show the tooltips. Boolean value with the default being true.]]></description>
</attribute>
<attribute>
<name>sortRowsCallback</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[A fully qualified class name to a custom SortRowsCallback implementation. Could also be a named type in the preferences. Used to sort the Collection of Beans or Collection of Maps.]]></description>
</attribute>
<attribute>
<name>sortable</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[Specify whether or not the table is sortable. Boolean value with the default being true.]]></description>
</attribute>
<attribute>
<name>state</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The table state to use when returning to a table. Acceptable values are default, notifyToDefault, persist, notifyToPersist.]]></description>
</attribute>
<attribute>
<name>stateAttr</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The table attribute used to invoke the state change of the table.]]></description>
</attribute>
<attribute>
<name>style</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The css inline style sheet.]]></description>
</attribute>
<attribute>
<name>styleClass</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The css class style sheet.]]></description>
</attribute>
<attribute>
<name>tableId</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The unique identifier for the table.]]></description>
</attribute>
<attribute>
<name>theme</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The theme to style the table. The default is eXtremeTable.]]></description>
</attribute>
<attribute>
<name>title</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The title of the table. The title will display above the table.]]></description>
</attribute>
<attribute>
<name>var</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[The name of the variable to hold the current row bean.]]></description>
</attribute>
<attribute>
<name>view</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[Generates the output. The default is the HtmlView to generate the HTML. Also used by the exports to generate XLS-FO, POI, and CSV.]]></description>
</attribute>
<attribute>
<name>width</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
<description><![CDATA[Width of the table.]]></description>
</attribute>
</tag>
从上面我们可以看到，先定义了table标签的实现类：org.extremecomponents.table.tag.TableTag，其作用是：
The container which holds all the main table information. Will also hold global information if needed. The table tag is copied into the Table and encapsulated in the Model.
一句话：保存table的信息及一些全局信息，通过table封装到Model中。
然后定义了table的一些属性，这些属性和org.extremecomponents.table.bean.Table一致。
public class Table extends Attributes {
private TableModel model;
private String action;
private Boolean autoIncludeParameters;
private String border;
private Boolean bufferView;
private String cellpadding;
private String cellspacing;
private Boolean filterable;
private String filterRowsCallback;
private String form;
private String imagePath;
private String interceptor;
private Object items;
private String locale;
private int maxRowsDisplayed;
private int medianRowsDisplayed;
private String method;
private String onInvokeAction;
private String retrieveRowsCallback;
private int rowsDisplayed;
private Boolean saveFilterSort;
private String scope;
private Boolean showExports;
private Boolean showPagination;
private Boolean showStatusBar;
private Boolean showTitle;
private Boolean showTooltips;
private String sortRowsCallback;
private Boolean sortable;
private String state;
private String stateAttr;
private String style;
private String styleClass;
private String tableId;
private String title;
private String theme;
private String var;
private String view;
private String width;
public Table(TableModel model) {
this.model = model;
}
// setter and getter
}
2. TableTag实现
我们来看一下TableTage如何实现table标签？首先：TableTage继承了TagSupport：
web容器执行自定义标签的过程如下
初始化时调用setPageContent()方法，完了在调用setParent方法
2.1 web容器首先执行自定义标签的开始标记，同时调用doStartTag方法。
2.2 如果doStartTag方法返回EVAL_BODY_INCLUDE，web容器在执行完标签体的内容后，会调用标签类得doAfterBody方法；
如果doStartTag方法返回SKIP_BODY,doAfterBody方法不会调用，web容器会直接调用标签类得doEndTag方法
2.3 如果doAfterBody方法被调用，并且方法返回EVAL_BODY_AGIN,web容器会再次执行标签体的内容；
如果doAfterBody方法返回SKIP_BODY,web容器会调用标签类的doEndTag方法
2.4 如果doEndTag方法返回EVAL_PAGE,web容器会执行标签后面的内容；
如果doEndTag方法返回SKIP_PAGE,web容器会忽略自定义标签后面的内容
public int doStartTag() throws JspException {
try {
// initialize the attributes
iterator = null;
pageContext.setAttribute(TableConstants.ROWCOUNT, "0");
// fire up the model with the context, preferences and messages
model = new TableModelImpl(new JspPageContext(pageContext), TagUtils.evaluateExpressionAsString("locale", this.locale, this, pageContext));
// make the table
Table table = new Table(model);
table.setAction(TagUtils.evaluateExpressionAsString("action", action, this, pageContext));
table.setAutoIncludeParameters(TagUtils.evaluateExpressionAsBoolean("autoIncludeParameters", this.autoIncludeParameters, this, pageContext));
table.setBorder(TagUtils.evaluateExpressionAsString("border", this.border, this, pageContext));
table.setBufferView(TagUtils.evaluateExpressionAsBoolean("bufferView", this.bufferView, this, pageContext));
table.setCellpadding(TagUtils.evaluateExpressionAsString("cellpadding", this.cellpadding, this, pageContext));
table.setCellspacing(TagUtils.evaluateExpressionAsString("cellspacing", this.cellspacing, this, pageContext));
table.setFilterable(TagUtils.evaluateExpressionAsBoolean("filterable", this.filterable, this, pageContext));
table.setFilterRowsCallback(TagUtils.evaluateExpressionAsString("filterRowsCallback", this.filterRowsCallback, this, pageContext));
table.setForm(TagUtils.evaluateExpressionAsString("form", this.form, this, pageContext));
table.setImagePath(TagUtils.evaluateExpressionAsString("imagePath", this.imagePath, this, pageContext));
table.setInterceptor(TagUtils.evaluateExpressionAsString("interceptor", this.interceptor, this, pageContext));
table.setItems(TagUtils.evaluateExpressionAsObject("items", this.items, this, pageContext));
table.setLocale(TagUtils.evaluateExpressionAsString("locale", this.locale, this, pageContext));
table.setMethod(TagUtils.evaluateExpressionAsString("method", this.method, this, pageContext));
table.setOnInvokeAction(TagUtils.evaluateExpressionAsString("onInvokeAction", this.onInvokeAction, this, pageContext));
table.setRetrieveRowsCallback(TagUtils.evaluateExpressionAsString("retrieveRowsCallback", this.retrieveRowsCallback, this, pageContext));
table.setRowsDisplayed(TagUtils.evaluateExpressionAsInt("rowsDisplayed", this.rowsDisplayed, this, pageContext));
table.setScope(TagUtils.evaluateExpressionAsString("scope", scope, this, pageContext));
table.setShowExports(TagUtils.evaluateExpressionAsBoolean("showExports", this.showExports, this, pageContext));
table.setShowPagination(TagUtils.evaluateExpressionAsBoolean("showPagination", this.showPagination, this, pageContext));
table.setShowStatusBar(TagUtils.evaluateExpressionAsBoolean("showStatusBar", this.showStatusBar, this, pageContext));
table.setShowTitle(TagUtils.evaluateExpressionAsBoolean("showTitle", this.showTitle, this, pageContext));
table.setShowTooltips(TagUtils.evaluateExpressionAsBoolean("showTooltips", this.showTooltips, this, pageContext));
table.setSortRowsCallback(TagUtils.evaluateExpressionAsString("sortRowsCallback", this.sortRowsCallback, this, pageContext));
table.setSortable(TagUtils.evaluateExpressionAsBoolean("sortable", this.sortable, this, pageContext));
table.setState(TagUtils.evaluateExpressionAsString("state", this.state, this, pageContext));
table.setStateAttr(TagUtils.evaluateExpressionAsString("stateAttr", this.stateAttr, this, pageContext));
table.setStyle(TagUtils.evaluateExpressionAsString("style", style, this, pageContext));
table.setStyleClass(TagUtils.evaluateExpressionAsString("styleClass", this.styleClass, this, pageContext));
table.setTableId(TagUtils.evaluateExpressionAsString("tableId", tableId, this, pageContext));
table.setTheme(TagUtils.evaluateExpressionAsString("theme", this.theme, this, pageContext));
table.setTitle(TagUtils.evaluateExpressionAsString("title", this.title, this, pageContext));
table.setVar(TagUtils.evaluateExpressionAsString("var", this.var, this, pageContext));
table.setView(TagUtils.evaluateExpressionAsString("view", this.view, this, pageContext));
table.setWidth(TagUtils.evaluateExpressionAsString("width", this.width, this, pageContext));
addTableAttributes(model, table);
model.addTable(table);
} catch (Exception e) {
throw new JspException("TableTag.doStartTag() Problem: " + ExceptionUtils.formatStackTrace(e));
}
return EVAL_BODY_INCLUDE;
}
/**
* Two things need to be accomplished here. First, need to iterate once over
* the columns to load up all the attributes. Second, need to iterate over
* the columns as many times as specified by the rowsDisplayed attribute so
* the columns row can be resolved. On each iteration over the columns the
* current bean in the collection is passed via the pageScope.
*/
public int doAfterBody() throws JspException {
try {
if (iterator == null) {
iterator = model.execute().iterator();
}
if (iterator != null && iterator.hasNext()) {
Object bean = iterator.next();
model.setCurrentRowBean(bean);
return EVAL_BODY_AGAIN;
}
} catch (Exception e) {
throw new JspException("TableTag.doAfterBody() Problem: " + ExceptionUtils.formatStackTrace(e));
}
return SKIP_BODY;
}
public int doEndTag() throws JspException {
try {
pageContext.getOut().println(model.getViewData());
} catch (Exception e) {
throw new JspException("TableTag.doEndTag() Problem: " + ExceptionUtils.formatStackTrace(e));
}
return EVAL_PAGE;
}
3. 深入追踪到TableModel
在doAfterBody()方法中调用了TableModel的excute方法：
public Collection execute() throws Exception {
//1. 查询记录
Collection rows = TableModelUtils.retrieveRows(this);
rows = new ArrayList(rows); // copy for thread safety
this.collectionOfBeans = rows;
//2. 过滤和排序记录
rows = TableModelUtils.filterRows(this, rows);
rows = TableModelUtils.sortRows(this, rows);
this.collectionOfFilteredBeans = rows;
// 3. 获取记录总数和pagesize
Integer totalRows = getTableHandler().getTotalRows();
int defaultRowsDisplayed = getTableHandler().getTable().getRowsDisplayed();
if (totalRows != null) {
//4. 设置记录总数和默认pagesize
limit.setRowAttributes(totalRows.intValue(), defaultRowsDisplayed);
} else {
limit.setRowAttributes(rows.size(), defaultRowsDisplayed);
}
if (logger.isDebugEnabled()) {
logger.debug(limit.toString());
}
//5. 获取本次显示的记录
rows = TableModelUtils.getCurrentRows(this, rows);
this.collectionOfPageBeans = rows;
//6. 视图显示
viewHandler.setView();
return rows;
}
4. 视图显示
默认定义了三种视图模式：extremetable.properties
table.view.compact=org.extremecomponents.table.view.CompactView
table.view.limit=org.extremecomponents.table.view.LimitView
table.view.html=org.extremecomponents.table.view.HtmlView
public void setView() throws Exception {
boolean isExported = model.getLimit().isExported();
String currentView = null;
if (isExported) {
currentView = model.getExportHandler().getCurrentExport().getView();
String preference = model.getPreferences().getPreference(PreferencesConstants.EXPORT_VIEW + currentView);
if (StringUtils.isNotBlank(preference)) {
currentView = preference;
}
} else {
currentView = model.getTableHandler().getTable().getView();
String preference = model.getPreferences().getPreference(PreferencesConstants.TABLE_VIEW + currentView);
if (StringUtils.isNotBlank(preference)) {
currentView = preference;
}
}
Class classDefinition = Class.forName(currentView);
this.view = (View) classDefinition.newInstance();
getView().beforeBody(model);
}
调用抽象类的beforeBody方法：
public final void beforeBody(TableModel model) {
this.model = model;
bufferView = model.getTableHandler().getTable().isBufferView();
if (bufferView) {
html = new HtmlBuilder();
} else {
html = new HtmlBuilder(model.getContext().getWriter());
}
formBuilder = new FormBuilder(html, model);
init(html, model);
formBuilder.formStart();
tableBuilder.themeStart();
beforeBodyInternal(model);
}
调用HtmlView的beforeBodyInternal处理
protected void beforeBodyInternal(TableModel model) {
toolbar(getHtmlBuilder(), getTableModel());
getTableBuilder().tableStart();
getTableBuilder().theadStart();
statusBar(getHtmlBuilder(), getTableModel());
getTableBuilder().filterRow();
getTableBuilder().headerRow();
getTableBuilder().theadEnd();
getTableBuilder().tbodyStart();
}
工具栏：
protected void toolbar(HtmlBuilder html, TableModel model) {
//layout 布局
new DefaultToolbar(html, model).layout();
}
左右布局格式：
public void layout() {
if (!showLayout(model)) {
return;
}
html.table(0).border("0").cellPadding("0").cellSpacing("0");
Table table = model.getTableHandler().getTable();
html.width(table.getWidth()).close();
html.tr(1).close();
// layout area left
columnLeft(html, model);
// layout area right
columnRight(html, model);
html.trEnd(1);
html.tableEnd(0);
html.newline();
}
布局的实现：
protected void columnLeft(HtmlBuilder html, TableModel model) {
html.td(2).close();
new TableBuilder(html, model).title();
html.tdEnd();
}
protected void columnRight(HtmlBuilder html, TableModel model) {
boolean showPagination = BuilderUtils.showPagination(model);
boolean showExports = BuilderUtils.showExports(model);
ToolbarBuilder toolbarBuilder = new ToolbarBuilder(html, model);
html.td(2).align("right").close();
html.table(2).border("0").cellPadding("0").cellSpacing("1").styleClass(BuilderConstants.TOOLBAR_CSS).close();
html.tr(3).close();
if (showPagination) {
html.td(4).close();
toolbarBuilder.firstPageItemAsImage();
html.tdEnd();
html.td(4).close();
toolbarBuilder.prevPageItemAsImage();
html.tdEnd();
html.td(4).close();
toolbarBuilder.nextPageItemAsImage();
html.tdEnd();
html.td(4).close();
toolbarBuilder.lastPageItemAsImage();
html.tdEnd();
html.td(4).close();
toolbarBuilder.separator();
html.tdEnd();
html.td(4).style("width:20px").close();
html.newline();
html.tabs(4);
toolbarBuilder.rowsDisplayedDroplist();
html.img();
html.src(BuilderUtils.getImage(model, BuilderConstants.TOOLBAR_ROWS_DISPLAYED_IMAGE));
html.style("border:0");
html.alt("Rows Displayed");
html.xclose();
html.tdEnd();
if (showExports) {
html.td(4).close();
toolbarBuilder.separator();
html.tdEnd();
}
}
if (showExports) {
Iterator iterator = model.getExportHandler().getExports().iterator();
for (Iterator iter = iterator; iter.hasNext();) {
html.td(4).close();
Export export = (Export) iter.next();
toolbarBuilder.exportItemAsImage(export);
html.tdEnd();
}
}
html.trEnd(3);
html.tableEnd(2);
html.newline();
html.tabs(2);
html.tdEnd();
}
状态栏和工具栏类似，就不一一赘述了。
5. 动作触发
以下一页来理解ectable中是如何触发事件的：
public void nextPageItemAsImage() {
ImageItem item = new ImageItem();
item.setTooltip(messages.getMessage(BuilderConstants.TOOLBAR_NEXT_PAGE_TOOLTIP));
item.setDisabledImage(BuilderUtils.getImage(model, BuilderConstants.TOOLBAR_NEXT_PAGE_DISABLED_IMAGE));
item.setImage(BuilderUtils.getImage(model, BuilderConstants.TOOLBAR_NEXT_PAGE_IMAGE));
item.setAlt(messages.getMessage(BuilderConstants.TOOLBAR_NEXT_PAGE_TEXT));
item.setStyle("border:0");
ToolbarItemUtils.buildNextPage(html, model, item);
}
下一页的构建
public static void buildNextPage(HtmlBuilder html, TableModel model, ToolbarItem item) {
int page = model.getLimit().getPage();
String action = new TableActions(model).getPageAction(page + 1);
item.setAction(action);
int totalPages = BuilderUtils.getTotalPages(model);
if (!BuilderUtils.isNextPageEnabled(page, totalPages)) {
item.disabled(html);
} else {
item.enabled(html, model);
}
}
触发动作，js实现
public String getPageAction(int page) {
StringBuffer action = new StringBuffer("javascript:");
action.append(getClearedExportTableIdParameters());
action.append(getFormParameter(TableConstants.PAGE, "" + page));
action.append(getOnInvokeAction());
return action.toString();
}
一个完整的table示例如下：
<table border="0" cellpadding="0" cellspacing="0" width="60%" >
<tr>
<td><span class="title" >persons</span></td>
<td align="right" >
<table border="0" cellpadding="0" cellspacing="1" class="toolbar" >
<tr>
<td><img src="/address-book/public/images/table/firstPageDisabled.gif" style="border:0" alt="第一页" /></td>
<td><img src="/address-book/public/images/table/prevPageDisabled.gif" style="border:0" alt="上一页" /></td>
<td><img src="/address-book/public/images/table/nextPageDisabled.gif" style="border:0" alt="下一页" /></td>
<td><img src="/address-book/public/images/table/lastPageDisabled.gif" style="border:0" alt="最后页" /></td>
<td><img src="/address-book/public/images/table/separator.gif" style="border:0" alt="Separator" /></td>
<td style="width:20px" >
<select name="ec_rd" onchange="javascript:document.forms.ec.ec_crd.value=this.options[this.selectedIndex].value;document.forms.ec.ec_p.value='1';document.forms.ec.setAttribute('action','/address-book/person/list');document.forms.ec.setAttribute('method','post');document.forms.ec.submit()" >
<option value="5" selected="selected">5</option><option value="50" >50</option><option value="100" >100</option>
</select><img src="/address-book/public/images/table/rowsDisplayed.gif" style="border:0" alt="Rows Displayed" /></td>
</tr>
</table>
</td>
</tr>
</table>
6. 小结：
eXtremeComponents为jsp开发table提供了比较好的支持，它的源码可以作为学习jsp tag的一个很好示例，研究该源码可以加深对jsp的理解，通过对上述源码进行合适的扩展后可以作为组件库使用。
参考文献：
1. http://liuna718-163-com.iteye.com/blog/1318991
2. http://www.51cto.com/specbook/11/57761.htm