自定义标签——带属性的标签

带属性的标签

步骤：
- 创建标签类；
- 配置标签；
- 设置标签属性，并使用：
示例代码：

package taglibclass;

import java.io.Writer;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.SimpleTagSupport;


public class QueryTag extends SimpleTagSupport {
    private String driver;
    private String username;
    private String password;
    private String url;
    private String sql;

    private Connection connection = null;
    private PreparedStatement ps = null;
    private ResultSet rs = null;
    private ResultSetMetaData rsmd = null;

    public void doTag() {

        try {
            Class.forName(driver);
            connection = DriverManager.getConnection(url, username, password);
            ps = connection.prepareStatement(sql);
            rs = ps.executeQuery();
            rsmd = rs.getMetaData();
            int columnCount = rsmd.getColumnCount();
            Writer out = getJspContext().getOut();
            out.write("<table border='1' width='400px'>");
            while (rs.next()) {
                out.write("<tr>");
                for (int j = 1; j <= columnCount; j++) {
                    out.write("<td>");
                    out.write(rs.getString(j));
                    out.write("</td>");
                }
                out.write("</tr>");
            }
            out.write("</table>");
        } catch (Exception e) {
            e.printStackTrace();
            try {
                throw new JspException("自定义标签错误" + e.getMessage());
            } catch (JspException e1) {
                e1.printStackTrace();
            }
        } finally {
            try{
                if(rs != null) 
                    rs.close();
                if(ps != null)
                    ps.close();
                if(connection != null)
                    connection.close();
            } catch(Exception e) {
                e.printStackTrace();
            }
            
        }
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public String getSql() {
        return sql;
    }

    public void setSql(String sql) {
        this.sql = sql;
    }

    public String getDriver() {
        return driver;
    }

    public void setDriver(String driver) {
        this.driver = driver;
    }

}

自定义标签配置：

<tag>
        <name>paramTag</name>
        <tag-class>taglibclass.QueryTag</tag-class>
  <!--设定自定义标签体为空，无此参数会抛出异常-->
        <body-content>empty</body-content>
            <!--设定自定义标签属性-->
        <attribute>
  <!--设定自定义标签属性名-->
            <name>driver</name>
  <!--设定自定义标签属性是否强制要求-->
            <required>true</required>
  <!--设定自定义标签属性是否支持JSP脚本-->
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>url</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>username</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>password</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>sql</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>

标签设置参数，并使用：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
    <%@ taglib uri="mytaglib/mytag" prefix="mytag" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<mytag:paramTag
    driver="com.mysql.jdbc.Driver"
    url="jdbc:mysql://localhost:3306/userlogin?useUnicode=true&characterEncoding=UTF-8&useSSL=false"
    username="root"
    password="root"
    sql="select * from user"/><br/>
</body>
</html>

自定义标签——带属性的标签

带属性的标签

猜你喜欢