JSP定制标记中的属性

对于任何自定义标签, 可能定义了太多属性。要定义属性, 你需要执行两个任务：

• 使用属性名称在TagHandler类中定义属性并定义setter方法
• 在TLD文件中的tag元素内定义attribute元素

让我们通过下面给出的标签来了解属性：

<m:cube number="4"></m:cube>

这里m是前缀, cube是标签名称, number是属性。

JSP自定义标记中属性的简单示例

在此示例中, 我们将使用多维数据集标记, 该标记返回任何给定数字的多维数据集。在这里, 我们为多维数据集标记定义了number属性。我们在这里使用三个文件：

• index.jsp
• CubeNumber.java
• mytags.tld

index.jsp

<%@ taglib uri="WEB-INF/mytags.tld" prefix="m" %>
Cube of 4 is: <m:cube number="4"></m:cube>

CubeNumber.java

package com.srcmini.taghandler;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;

public class CubeNumber extends TagSupport{
private int number;
	
public void setNumber(int number) {
	this.number = number;
}

public int doStartTag() throws JspException {
	JspWriter out=pageContext.getOut();
	try{
		out.print(number*number*number);
	}catch(Exception e){e.printStackTrace();}
	
	return SKIP_BODY;
}
}

mytags.tld

<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE taglib
        PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
        "http://java.sun.com/j2ee/dtd/web-jsptaglibrary_1_2.dtd">

<taglib>
  <tlib-version>1.0</tlib-version>
  <jsp-version>1.2</jsp-version>
  <short-name>simple</short-name>
  <uri>http://tomcat.apache.org/example-taglib</uri>
  <description>A simple tab library for the examples</description>

  <tag>
    <name>cube</name>
    <tag-class>com.srcmini.taghandler.CubeNumber</tag-class>
    <attribute>
    <name>number</name>
    <required>true</required>
    </attribute>
  </tag>
</taglib>

输出量

Cube of 4 is: 64

数据库的JSP自定义标签属性示例

让我们创建一个自定义标签, 该标签针对给定的表名和ID打印表的特定记录。

因此, 你必须在标记处理程序类中具有两个属性。

PrintRecord.java

package com.srcmini;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;
import java.sql.*;

public class PrintRecord extends TagSupport{
private String id;
private String table;

public void setId(String id) {
	this.id = id;
}
public void setTable(String table) {
	this.table = table;
}

public int doStartTag()throws JspException{
	JspWriter out=pageContext.getOut();
	try{ 
		Class.forName("oracle.jdbc.driver.OracleDriver");
		Connection con=DriverManager.getConnection(
                 "jdbc:oracle:thin:@localhost:1521:xe", "system", "oracle");
		PreparedStatement ps=con.prepareStatement("select * from "+table+" where id=?");
		ps.setInt(1, Integer.parseInt(id));
		ResultSet rs=ps.executeQuery();
		if(rs!=null){
		ResultSetMetaData rsmd=rs.getMetaData();
		int totalcols=rsmd.getColumnCount();
		//column name
		out.write("<table border='1'>");
		out.write("<tr>");
		for(int i=1;i<=totalcols;i++){
			out.write("<th>"+rsmd.getColumnName(i)+"</th>");
		}
		out.write("</tr>");
		//column value
		
		if(rs.next()){
			out.write("<tr>");
				for(int i=1;i<=totalcols;i++){
				out.write("<td>"+rs.getString(i)+"</td>");
			}
			out.write("</tr>");
				
		}else{
			out.write("Table or Id doesn't exist");
		}
		out.write("</table>");
		
		}
		con.close();
	}catch(Exception e){System.out.println(e);}
	return SKIP_BODY;
}
}

m.tld

<?xml version="1.0" encoding="ISO-8859-1" ?>  
<!DOCTYPE taglib  
        PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"  
    "http://java.sun.com/j2ee/dtd/web-jsptaglibrary_1_2.dtd">  
  
<taglib>

  <tlib-version>1.2</tlib-version>
  <jsp-version>2.0</jsp-version>
  <short-name>c</short-name>
  <uri>srcmini</uri>

<tag>
<name>printRecord</name>
<tag-class>com.srcmini.PrintRecord</tag-class>
<attribute>
<name>id</name>
<required>true</required>
</attribute>
<attribute>
<name>table</name>
<required>true</required>
</attribute>

</tag>
</taglib>

index.jsp

<%@ taglib uri="srcmini" prefix="j" %>
<j:printRecord table="user874" id="1"></j:printRecord>

输出量

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