public static final int EVAL_BODY_AGAIN = 2;
<<interface Tag>>
public static final int SKIP_BODY = 0;
public static final int EVAL_BODY_INCLUDE = 1;
public static final int SKIP_PAGE = 5;
public static final int EVAL_PAGE = 6;
0、1給doStartTag()回傳
回傳0就調用doEndTag()
回傳1就調用doAfterBody()
0、2給doAfterBody()回傳
回傳0就調用doEndTag()
回傳2就調用自己，一直到回傳0為止
5、6給doEndTag()回傳
回傳5表示立即停止，忽略之後的頁面，但會將目前的輸出回傳到瀏覽器
回傳6表示正常結束
release()：將資源全部釋放，修改後不重啟瀏覽器，過一下子就會直接調用
※SKIP_BODY、EVAL_BODY_INCLUDE
※AttrTag.java
public class AttrTag extends TagSupport {
private String scope;
private String content;
// 這兩個屬性都給setter即可
@Override
public int doStartTag() throws JspException {
System.out.println("doStartTag");
Object value = null;
if ("P".equals(scope)) {
value = pageContext.getAttribute(content, PageContext.PAGE_SCOPE);
}
if ("R".equals(this.scope)) {
value = pageContext.getAttribute(content, PageContext.REQUEST_SCOPE);
}
if ("S".equals(this.scope)) {
value = pageContext.getAttribute(content, PageContext.SESSION_SCOPE);
}
if ("A".equals(this.scope)) {
value = pageContext.getAttribute(content, PageContext.APPLICATION_SCOPE);
}
if (value == null) {
return SKIP_BODY;
} else {
return EVAL_BODY_INCLUDE;
}
}
※attr.tld
<tag> <name>displayScope</name> <tag-class>attr.AttrTag</tag-class> <body-content>JSP</body-content> <attribute> <name>scope</name> <required>true</required> <rtexprvalue>true</rtexprvalue> </attribute> <attribute> <name>content</name> <required>true</required> <rtexprvalue>true</rtexprvalue> </attribute> </tag>
body content變成JSP
※attr.jsp
<%
String scope = "P";
if ("P".equals(scope)) {
pageContext.setAttribute("ooo", scope);
} else if ("R".equals(scope)) {
request.setAttribute("ooo", scope);
} else if ("S".equals(scope)) {
session.setAttribute("ooo", scope);
} else if ("A".equals(scope)) {
application.setAttribute("ooo", scope);
}
%>
<bruce:displayScope scope="<%=scope%>" content="ooo">
<h1>範圍：<%=scope%></h1>
<h1>pageScope內容是${pageScope.ooo}</h1>
<h2>requestScope內容是${requestScope.ooo}</h2>
<h3>sessionScope內容是${sessionScope.ooo}</h3>
<h4>applicationScope內容是${applicationScope.ooo}</h4>
</bruce:displayScope>
※如果scope不輸入PRSA其中一個，就會調用SKIP_BODY
※SKIP_BODY、EVAL_BODY_AGAIN
※jsp
<%
List<String> list = new ArrayList<String>();
list.add("A1");
list.add("B2");
list.add("C3");
request.setAttribute("ooo", list);
%>
<bruce:iterate content="ooo" id="abc">
${abc}<br/>
</bruce:iterate>
※
※tld
<tag> <name>iterate</name> <tag-class>attr.AttrHaveContent2</tag-class> <body-content>JSP</body-content> <attribute> <name>content</name> <required>true</required> <rtexprvalue>true</rtexprvalue> </attribute> <attribute> <name>id</name> <required>true</required> <rtexprvalue>true</rtexprvalue> </attribute> </tag>
※
※java
public class AttrHaveContent extends TagSupport {
private String content;
private Iterator<?> it;
public void setContent(String content) {
this.content = content;
}
@Override
public int doStartTag() throws JspException {
System.out.println("doStartTag");
Object value = pageContext.getAttribute(content, PageContext.REQUEST_SCOPE);
System.out.println("value=" + value);
if (value == null) {
return SKIP_BODY;
} else {
List<?> x = ((List<?>) value);
// Set<String> x = ((Map<String, Object>) value).keySet();
// Collection<Object> x = ((Map<String, Object>) value).values();
it = x.iterator();
if (it.hasNext()) {
pageContext.setAttribute(id, it.next());
return EVAL_BODY_INCLUDE;
}
return SKIP_BODY;
}
}
@Override
public int doEndTag() throws JspException {
System.out.println("doEndTag");
return SKIP_PAGE;
}
@Override
public int doAfterBody() throws JspException {
System.out.println("doAfterBody");
if (it.hasNext()) {
pageContext.setAttribute(id, it.next());
return EVAL_BODY_AGAIN;
} else {
return SKIP_BODY;
}
}
}
※TagSupport.java裡有個屬性是id，是protected，所以可以不用宣告id，但要用時還是要在tld裡定義
※setValue、getValues
List<?> x = ((List<?>) value);
for (int i = 0; i < x.size(); i++) {
String s = (String) x.get(i);
setValue(s.substring(1), "x");
}
enu = getValues();
if (enu.hasMoreElements()) {
pageContext.setAttribute(id, enu.nextElement());
return EVAL_BODY_INCLUDE;
}
※TagSupport還有個Hashtable叫values，但它是private，但有setValue和getValues可以塞進去，getValues回傳值是Enumeration，和Iterator很像
※doAfterBody也改成Enumeration就可以取到值了，取到的是setValue的Key值
※SKIP_PAGE、EVAL_PAGE
※jsp
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <%@taglib uri="attrHaveContent" prefix="bruce"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head></head> <body> <bruce:endTagTest /> ooo </body> </html>
※
※web.xml
<jsp-config> <taglib> <taglib-uri>attrHaveContent</taglib-uri> <taglib-location>/WEB-INF/AttrHave.xml</taglib-location> </taglib> </jsp-config>
※
※tld
<taglib version="2.1" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"> <tlib-version>1.0</tlib-version> <short-name>ht</short-name> <tag> <name>endTagTest</name> <tag-class>attr.AttrHaveContent</tag-class> <body-content>empty</body-content> </tag> </taglib>
※
※java
public class AttrHaveContent extends TagSupport {
@Override
public int doEndTag() throws JspException {
System.out.println("doEndTag");
JspWriter out = this.pageContext.getOut();
try {
out.println("xxx");
} catch (IOException e) {
e.printStackTrace();
}
return SKIP_PAGE;
}
}
※回傳SKIP_PAGE時，不會印出ooo
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