jsp2自定义标签+属性

前面说过jsp2自定义标签如果要加入属性需要设置属性的getter和setter方法。代码如下：

public class GetParam extends SimpleTagSupport {
    private String driver;
    private String url;
    private String user;
    private String pwd;
    private String sql;
    private Connection conn = null;;
    private Statement stm = null;;
    private ResultSet rs = null;

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

    public String getDriver() {
        return this.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 getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    public String getSql() {
        return sql;
    }

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

    @Override
    public void doTag() throws JspException, IOException {
        // TODO Auto-generated method stub
        try {
            // 注册驱动
            Class.forName(driver);
            // 建立连接
            conn = DriverManager.getConnection(url, user, pwd);
            stm = conn.createStatement();
            rs = stm.executeQuery(sql);
            // 获取页面输出流
            Writer out = getJspContext().getOut();
            // 设置表格
            out.write("<table border='1' width='300'>");
            // 遍历
            while (rs.next()) {
                out.write("<tr>");
                for (int i = 1; i < rs.getMetaData().getColumnCount(); i++) {
                    out.write("<td>");
                    out.write(rs.getString(i));
                    out.write("</td>");
                }
                out.write("</tr>");
            }
            out.write("</table>");

        } catch (SQLException | ClassNotFoundException ex) {

            // TODO: handle exception
            ex.printStackTrace();
            throw new JspException("自定义标签错误" + ex.getMessage());
        } finally {
            try {
                if (rs != null) {
                    rs.close();
                }
                if (stm != null) {
                    stm.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                // TODO: handle exception
                e.printStackTrace();
            }
        }
    }
}

接下来配置tld文件，对于有属性的标签，需要在<tag>元素下增加<attribute>子元素。在<attribute>下有三个元素，

第一个是name:设置属性名，第二个是required：该属性是否为必须属性，第三个是fragment：该属性是否支持JSP脚本，表达式等动态内容。

在配置<attribute>下面的name时候，一定要和属性名对应，不然会报错"Unable to find setter method for attribute: XXX"，tld文件完整代码如下：

<?xml version="1.0" encoding="GBK" ?>
<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">
    <!-- 描述 -->
    <description>A tag library exercising SimpleTag handlers.</description>
    <!-- 版本 -->
    <tlib-version>1.0</tlib-version>
    <!-- 短名 -->
    <short-name>gotparam</short-name>
    <!-- 指定标签库URI -->
    <uri>http://tomcat.apache.org/gotparam</uri>
    <tag>
        <description>Outputs Hello, World</description>
        <!-- 标签库名字 -->
        <name>GetParam</name>
        <!-- 标签处理类 -->
        <tag-class>lee.GetParam</tag-class>
        <!-- 标签体内容 -->
        <body-content>empty</body-content>
        <!-- 标签属性:driver -->
        <attribute>
            <name>driver</name>
            <required>true</required>
            <fragment>true</fragment>
        </attribute>
        <!-- 标签属性:url -->
        <attribute>
            <name>url</name>
            <required>true</required>
            <fragment>true</fragment>
        </attribute>
        <!-- 标签属性:user -->
        <attribute>
            <name>user</name>
            <required>true</required>
            <fragment>true</fragment>
        </attribute>
        <!-- 标签属性:pwd -->
        <attribute>
            <name>pwd</name>
            <required>true</required>
            <fragment>true</fragment>
        </attribute>
        <!-- 标签属性:sql -->
        <attribute>
            <name>sql</name>
            <required>true</required>
            <fragment>true</fragment>
        </attribute>
    </tag>
</taglib>

最后新建一个jsp文件测试标签，代码如下：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib uri="http://tomcat.apache.org/gotparam" prefix="gotparam"%>
<!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>
    <gotparam:GetParam user="root" url="jdbc:mysql://localhost:3306/house"
        driver="com.mysql.jdbc.Driver" pwd="123456" sql="select * from house" />
</body>
</html>