我一直在玩这个代码几个小时,我无法确定为什么我的标签似乎什么也没做。
lab08.jspx 只是简单地输出Set Body
在lab08J.html 的字段中输入的任何内容,似乎完全忽略了该friend
条目。代码如下。
lab08J.html
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/1999/xhtml
http://www.w3.org/2002/08/xhtml/xhtml1-strict.xsd">
<head><title>lab08J.html</title><head>
<body>
<form action="lab08J.jspx">
Set Friend:<input type="text" name="friend"/>
<p>Set Body:<input type="text" name="body"/>
<input type="submit"/>
</form>
</body>
</html>
lab08J.jspx
<html xmlns:j="http://ets.com/tags/j"
xmlns:jsp="http://java.sun.com/JSP/Page">
<jsp:output omit-xml-declaration="true" />
<jsp:directive.page contentType="text/html" />
<head><title>lab08.jspx</title></head>
<body><j:myTag friend="${param.friend}">${param.body}</j:myTag>
</body>
</html>
web.xml
<?xml version="1.0" ?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
</web-app>
myTags.tld
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
version="2.0">
<tlib-version>1.0</tlib-version>
<short-name>lab08Jtaglib</short-name>
<uri>http://ets.com/tags/j</uri>
<tag>
<name>myTag</name>
<tag-class>webcert.ch08.lab08J.MyTag</tag-class>
<body-content>JSP</body-content>
<attribute>
<name>friend</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
我的标签.java
package webcert.ch08.lab08J;
import java.io.IOException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.BodyContent;
import javax.servlet.jsp.tagext.BodyTagSupport;
import javax.servlet.jsp.tagext.IterationTag;
public class MyTag extends BodyTagSupport{
private PageContext pageContext;
private BodyTagSupport parent;
private String friend;
private BodyContent bc = getBodyContent();
public void setPageContext(PageContext pageContext){
super.setPageContext(pageContext);
log("setPageContext()");
}
public void setParent(BodyTagSupport parent){
super.setParent(parent);
log("setParent()");
}
public void setFriend(String friend)throws Exception{
this.friend = friend;
log("setFriend() as " + friend);
JspWriter out = pageContext.getOut();
out.write("setFriend as " + friend);
}
public int doStartTag(){
log("doStartTag()");
return BodyTagSupport.EVAL_BODY_BUFFERED;
}
public void setBodyContent(BodyContent bc){
super.setBodyContent(bc);
log("setBodyContent()");
}
public void doInitBody(){
log("doInitBody()");
}
public int doAfterBody(){
log("doAfterBody()");
try{
bc.write("Meet my friend " + friend);
}
catch(IOException ioe){
ioe.printStackTrace();
}
return IterationTag.EVAL_BODY_AGAIN;
}
public int doEndTag(){
log("doEndTag()");
try{
bc.writeOut(bc.getEnclosingWriter());
}
catch(IOException ioe){
ioe.printStackTrace();
}
return BodyTagSupport.EVAL_PAGE;
}
public void release(){
System.out.println("release()");
super.release();
}
protected void log(String s){
try {
bc.write(s);
} catch (IOException e) {
e.printStackTrace();
}
}
}