本文介绍如何使用JSP自定义标签进行数据库操作及字符串转换。包括读取、插入、删除数据库记录，并实现了字符串大小写的转换。
范例一：使用自定义Tag去读数据库中的信息
TagDB.java代码如下
package tag.test;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;
import java.sql.*;
public class TagDB extends TagSupport
{
Connection connection=null;
Statement statement=null;
ResultSet rset=null;
public TagDB()
{
try
{
Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");
}
catch(ClassNotFoundException e)
{
e.printStackTrace();
}
}
public int doStartTag()throws JspTagException
{
return EVAL_BODY_INCLUDE;
}
public int doEndTag()throws JspTagException
{
try
{
JspWriter out=pageContext.getOut();
connection=DriverManager.getConnection("jdbc:sqlserver://localhost;databaseName=pubs;user=sa;password=1234");
statement=connection.createStatement();
rset=statement.executeQuery("select * from authors");
out.print("以下使用Tag输出作者的基本信息");
out.print("
"); out.print("
");
}
catch(Exception e)
{
e.printStackTrace();
}
return EVAL_PAGE;
}
}
author.tld描述文件如下
<?xml version="1.0" encoding="ISO-8859-1"?><taglib><tlib-version>1.2</tlib-version><jsp-version>1.2</jsp-version><short-name>DB</short-name><description>
this taglib provides tag to show date
</description><tag><name>DBShow</name><tag-class>tag.test.TagDB</tag-class><body-content>empty</body-content></tag></taglib>
web.xml文件内容如下
<?xml version="1.0" encoding="ISO-8859-1"?><web-app><display-name>welcome to Tomcat</display-name><description>
Welcome to Tomcat
</description><taglib><taglib-uri>DB</taglib-uri><taglib-location>/WEB-INF/author.tld</taglib-location></taglib></web-app>
tagTest.jsp文件如下
<dbshow></dbshow>
范例二：使用Tag标签向数据库中查入数据，插入成功后将所有记录显示出来.
InfoTagDB.java 代码如下
package tag.test;
import java.io.*;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.sql.*;
public class InfoTagDB extends TagSupport
{
String strNumber;
String strName;
int strNum;
Connection connection=null;
Statement statement=null;
public InfoTagDB()
{
try
{
Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");
}
catch(ClassNotFoundException e)
{
e.printStackTrace();
}
}
public void setStrNumber(String strNumber)
{
this.strNumber=strNumber;
}
public void setStrName(String strName)
{
this.strName=strName;
}
public void setStrNum(int strNum)
{
this.strNum=strNum;
}
public int doStartTag()throws JspTagException
{
JspWriter out=pageContext.getOut();
try
{
connection=DriverManager.getConnection("jdbc:sqlserver://localhost;databaseName=pubs;user=sa;password=1234");
statement=connection.createStatement();
String sql="insert into authors(au_id,au_lname,au_fname,phone,address,city) values('"+au_id+"','"+au_lname+"','"+au_fname+"','"+phone+"','"+address+"','"+city + "')";
int i=statement.executeUpdate(sql);
if(i>0)
{
out.print("插入成功");
}
else
{
out.print("插入失败");
}
statement.close();
connection.close();
}
catch(Exception e)
{
e.printStackTrace();
}
return SKIP_BODY;
}
}
insert.tld标签描述文件如下
<?xml version="1.0" encoding="ISO-8859-1"?><taglib><tlib-version>1.2</tlib-version><jsp-version>1.2</jsp-version><shor-name>mytag</shor-name><description>the info test example</description><tag><name>insert</name><tag-class>tag.test.InfoTagDB</tag-class><body-content>empty</body-content><attribute><name>au_id</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute><attribute><name>au_lname</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute><attribute><name>au_fname</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute><attribute><name>phone</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute><attribute><name>address</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute><attribute><name>city</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute></tag></taglib>
web.xml配置文件如下
<?xml version="1.0" encoding="ISO-8859-1"?><web-app><display-name>welcome to Tomcat</display-name><description>
Welcome to Tomcat
</description><taglib><taglib-uri>DBInsert</taglib-uri><taglib-location>/WEB-INF/insert.tld</taglib-location></taglib><taglib><taglib-uri>DB</taglib-uri><taglib-location>/WEB-INF/author.tld</taglib-location></taglib></web-app>
tagTest.jsp文件如下
<insert au_id="888_666" au_lname="jane" au_fname="peng" phone="15853208264" address="中国海洋大学" city="青岛"></insert><dbshow></dbshow>
对于tagTest.jsp文件中的第二个标签是范例一TagDB.java中的代码，大家可以参考。
范例三：使用Tag删除数据库中的记录,删除后将所有数据库中的内容显示出来
TagDelete.java代码如下
package tag.test;
import java.sql.*;
import java.io.*;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
public class TagDelete extends TagSupport
{
String au_id;
Connection connection=null;
Statement statement=null;
public TagDelete()
{
try
{
Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");
}
catch(ClassNotFoundException e)
{
e.printStackTrace();
}
}
public void setAu_id(String s)
{
this.au_id=s;
}
public int doStartTag()throws JspTagException
{
try
{
JspWriter out=pageContext.getOut();
connection=DriverManager.getConnection("jdbc:sqlserver://localhost;databaseName=pubs;user=sa;password=1234");
statement=connection.createStatement();
String sql="delete * from authors where au_id='"+au_id+"'";
int i=statement.executeUpdate(sql);
if(i>0)
{
out.print("删除成功
"); } else { out.print("删除失败
"); } statement.close(); connection.close(); } catch(Exception e) { e.printStackTrace(); } return SKIP_BODY; } public int doEndTag()throws JspException { return EVAL_PAGE; } } delete.tld标签描述文件如下 <?xml version="1.0" encoding="ISO-8859-1"?><taglib><tlib-version>1.2</tlib-version><jsp-version>1.2</jsp-version><shor-name>Deltag</shor-name><description>the info test example</description><tag><name>delete</name><tag-class>tag.test.TagDelete</tag-class><body-content>empty</body-content><attribute><name>au_id</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute></tag></taglib> web.xml配置文件如下 <?xml version="1.0" encoding="ISO-8859-1"?><web-app><display-name>welcome to Tomcat</display-name><description> Welcome to Tomcat </description><taglib><taglib-uri>DBInsert</taglib-uri><taglib-location>/WEB-INF/insert.tld</taglib-location></taglib><taglib><taglib-uri>DB</taglib-uri><taglib-location>/WEB-INF/author.tld</taglib-location></taglib><taglib><taglib-uri>Deltag</taglib-uri><taglib-location>/WEB-INF/delete.tld</taglib-location></taglib></web-app> tagTest.jsp测试代码如下 <delete au_id="172-32-8886"></delete><dbshow></dbshow> 对于tagTest.jsp文件中的第二个标签是范例一TagDB.java中的代码，大家可以参考 范例五：使用自定义标签实现字符串的大小写转化。 ConvertTest.java代码如下 package tag.test; import java.io.*; import javax.servlet.jsp.*; import javax.servlet.jsp.tagext.*; public class ConvertTest extends BodyTagSupport { public int doAfterBody()throws JspException { try { BodyContent body=getBodyContent(); JspWriter out=body.getEnclosingWriter(); String text=body.getString();//获取标签中的内容 if(text!=null) { out.print(text.toLowerCase()); } } catch(Exception e) { e.printStackTrace(); } return SKIP_BODY; } } convert.tld标签描述文件如下 <?xml version="1.0" encoding="ISO-8859-1"?><taglib><tlib-version>1.2</tlib-version><jsp-version>1.2</jsp-version><shor-name>mytag</shor-name><description>the info test example</description><tag><name>Convert</name><tag-class>tag.test.ConvertTest</tag-class><body-content>jsp</body-content></tag></taglib> web.xml配置文件如下 <?xml version="1.0" encoding="ISO-8859-1"?><web-app><display-name>welcome to Tomcat</display-name><description> Welcome to Tomcat </description><taglib><taglib-uri>mytag</taglib-uri><taglib-location>/WEB-INF/convert.tld</taglib-location></taglib></web-app> testTag.jsp测试文件如下 <convert> Hello FRIEND! THIS A PROGRAMM TO CONVERT BIG CHAR TO SMALL CHAR; </convert>
"); out.print("
| au_id | au_lname | au_fname | phone | address | city |
| "+rset.getString(1)+" | "+rset.getString(2)+" | "+rset.getString(3)+" | "+rset.getString(4)+" | "+rset.getString(5)+" | "+rset.getString(6)+" |
"); } else { out.print("删除失败
"); } statement.close(); connection.close(); } catch(Exception e) { e.printStackTrace(); } return SKIP_BODY; } public int doEndTag()throws JspException { return EVAL_PAGE; } } delete.tld标签描述文件如下 <?xml version="1.0" encoding="ISO-8859-1"?><taglib><tlib-version>1.2</tlib-version><jsp-version>1.2</jsp-version><shor-name>Deltag</shor-name><description>the info test example</description><tag><name>delete</name><tag-class>tag.test.TagDelete</tag-class><body-content>empty</body-content><attribute><name>au_id</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute></tag></taglib> web.xml配置文件如下 <?xml version="1.0" encoding="ISO-8859-1"?><web-app><display-name>welcome to Tomcat</display-name><description> Welcome to Tomcat </description><taglib><taglib-uri>DBInsert</taglib-uri><taglib-location>/WEB-INF/insert.tld</taglib-location></taglib><taglib><taglib-uri>DB</taglib-uri><taglib-location>/WEB-INF/author.tld</taglib-location></taglib><taglib><taglib-uri>Deltag</taglib-uri><taglib-location>/WEB-INF/delete.tld</taglib-location></taglib></web-app> tagTest.jsp测试代码如下 <delete au_id="172-32-8886"></delete><dbshow></dbshow> 对于tagTest.jsp文件中的第二个标签是范例一TagDB.java中的代码，大家可以参考 范例五：使用自定义标签实现字符串的大小写转化。 ConvertTest.java代码如下 package tag.test; import java.io.*; import javax.servlet.jsp.*; import javax.servlet.jsp.tagext.*; public class ConvertTest extends BodyTagSupport { public int doAfterBody()throws JspException { try { BodyContent body=getBodyContent(); JspWriter out=body.getEnclosingWriter(); String text=body.getString();//获取标签中的内容 if(text!=null) { out.print(text.toLowerCase()); } } catch(Exception e) { e.printStackTrace(); } return SKIP_BODY; } } convert.tld标签描述文件如下 <?xml version="1.0" encoding="ISO-8859-1"?><taglib><tlib-version>1.2</tlib-version><jsp-version>1.2</jsp-version><shor-name>mytag</shor-name><description>the info test example</description><tag><name>Convert</name><tag-class>tag.test.ConvertTest</tag-class><body-content>jsp</body-content></tag></taglib> web.xml配置文件如下 <?xml version="1.0" encoding="ISO-8859-1"?><web-app><display-name>welcome to Tomcat</display-name><description> Welcome to Tomcat </description><taglib><taglib-uri>mytag</taglib-uri><taglib-location>/WEB-INF/convert.tld</taglib-location></taglib></web-app> testTag.jsp测试文件如下 <convert> Hello FRIEND! THIS A PROGRAMM TO CONVERT BIG CHAR TO SMALL CHAR; </convert>
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