JSP 自定义标签（备忘）

目标：在jsp页面上通过自定义标签，查询数据库。

 

package org.vv.taglib;

import java.io.IOException;
import java.io.Writer;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;

import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.tagext.TagSupport;

public class QueryTag extends TagSupport {

    private static final long serialVersionUID = 1L;
    // 标签的属性
    private String driver;
    private String url;
    private String user;
    private String password;
    private String sql;
    // 执行数据库访问的对象
    private Connection conn = null;
    private Statement stmt = null;
    private ResultSet rs = null;
    private ResultSetMetaData rsmd = null;

    // 标签属性 driver url user password sql 的getter/setter方法
    public String getDriver() {
        return driver;
    }

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

    public String getUrl() {
        return url;
    }

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

    public String getUser() {
        return user;
    }

    public void setUser(String user) {
        this.user = user;
    }

    public String getPassword() {
        return password;
    }

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

    public String getSql() {
        return sql;
    }

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

    // 标签处理
    public int doEndTag() throws JspTagException {
        // 注册驱动
        try {
            Class.forName(driver);
            // 获取数据库连接
            conn = DriverManager.getConnection(url, user, password);
            // 创建Statement对象
            stmt = conn.createStatement();
            // 执行查询
            rs = stmt.executeQuery(sql);
            rsmd = rs.getMetaData();
            // 获取列数目
            int columnCount = rsmd.getColumnCount();
            // 获取页面输出流
            Writer out = pageContext.getOut();
            // 在页面输出表格
            out.write("<table border='1' bgColor='9999cc'>");
            // 遍历结果集
            out.write("<tr>");
            for (int i=0;i<rs.getMetaData().getColumnCount();i++){
            	out.write("<td>");
            	out.write(rs.getMetaData().getColumnName(i+1)); 
            	out.write("</td>");
            }
            out.write("</tr>");
            while (rs.next()) {
                out.write("<tr>");
                // 逐列输出查询到的数据
                for (int i = 1; i <= columnCount; i++) {
                    out.write("<td>");
                    out.write(rs.getString(i));
                    out.write("</td>");
                }
                out.write("</tr>");
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            destroy();
        }

        return EVAL_PAGE;
    }

    // 销毁标签前调用的方法
    public void destroy() {
        // 关闭结果集
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        // 关闭Statement
        if (stmt != null) {
            try {
                stmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        // 关闭数据库连接
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

 

 

在 WebRoot\WEB-INF 目录下添加文件 query.tld

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN" "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd" >
<taglib>
    <tlib-version>1.0</tlib-version>
    <jsp-version>2.0</jsp-version>
    <short-name>query</short-name>
    <tag>
        <!-- 配置标签名 -->
        <name>query</name>
        <!-- 配置标签处理类 -->
        <tag-class>org.vv.taglib.QueryTag</tag-class>
        <!-- 配置标签体为空 -->
        <body-content>empty</body-content>
        <!-- 配置标签属性 driver -->
        <attribute>
            <name>driver</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <!-- 配置标签属性 url -->
        <attribute>
            <name>url</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <!-- 配置标签属性 user -->
        <attribute>
            <name>user</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <!-- 配置标签属性 password -->
        <attribute>
            <name>password</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <!-- 配置标签属性 sql -->
        <attribute>
            <name>sql</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
</taglib>

 

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.4"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    <jsp-config>
        <taglib>
            <taglib-uri>query</taglib-uri>
            <taglib-location>/WEB-INF/query.tld</taglib-location>
        </taglib>
    </jsp-config>
</web-app>

 

jsp 页面中的调用方法

<myquery:query driver="com.microsoft.jdbc.sqlserver.SQLServerDriver"
url="jdbc:microsoft:sqlserver://192.168.0.88:1433;DatabaseName=directorMail"
user="user" password="password" sql="select * from mailInfo" />