自定义tag

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(""); while(rset.next()) { out.print(""); } 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)+"

"); } 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>