1初始化参数init-param
init-param是配置在web.xml的<servlet>标签里的，也就是说，是归该servlet单独所有的。
实例
<servlet>
<servlet-name>ContextParamServlet</servlet-name>
<servlet-class>com.servlet.ContextParamServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>InitParamServlet</servlet-name>
<servlet-class>com.servlet.InitParamServlet</servlet-class>
<init-param>
<param-name>harry</param-name>
<param-value>3324</param-value>
</init-param>
<init-param>
<param-name>kitty</param-name>
<param-value>3124</param-value>
</init-param>
<init-param>
<param-name>rixiang</param-name>
<param-value>1992</param-value>
</init-param>
</servlet>
servlet程序中读取：
package com.servlet; import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration; import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; public class InitParamServlet extends HttpServlet { private static final long serialVersionUID = 1L; public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException,IOException{ response.setCharacterEncoding("UTF-8");
request.setCharacterEncoding("UTF-8"); response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println(" <HEAD><TITLE>请登录查看 Notice 文件</TITLE></HEAD>");
out.println("<style>body, td, div {font-size:12px; }</style>");
out.println(" <BODY>"); out.println("<form action='" + request.getRequestURI() + "' method='post'>");
out.println("帐号：<input type='text' name='username' style='width:200px; '> <br/>");
out.println("密码：<input type='password' name='password' style='width:200px; '> <br/><br/>");
out.println("<input type='submit' value=' 登录 '>");
out.println("</form>"); out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
} public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException,IOException{
String username = request.getParameter("username");
String password = request.getParameter("password");
@SuppressWarnings("rawtypes")
Enumeration params = this.getInitParameterNames();
while(params.hasMoreElements()){
String usernameParam = (String)params.nextElement();
String passnameParam = this.getInitParameter(usernameParam);
if(usernameParam.equalsIgnoreCase(username)
&& passnameParam.equals(password)){
request.getRequestDispatcher("/WEB-INF/notice.html").forward(request, response);
return;
}
}
this.doGet(request, response);
}
}
效果：
2上下文参数，context-param
context-param是所有servlet公有的
<context-param>
<param-name>upload folder</param-name>
<param-value>attachment</param-value>
</context-param>
<context-param>
<param-name>allowed file type</param-name>
<param-value>.gif,.jpg,.bmp</param-value>
</context-param>
servlet程序读取：
package com.servlet; import java.io.IOException;
import java.io.PrintWriter; import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; public class ContextParamServlet extends HttpServlet{
private static final long serialVersionUID = 1L; public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException,IOException{
response.setCharacterEncoding("UTF-8");
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println(" <HEAD><TITLE>读取文档参数</TITLE></HEAD>");
out.println(" <link rel='stylesheet' type='text/css' href='../css/style.css'>");
out.println(" <BODY>");
out.println("<div align=center><br/>");
out.println("<fieldset style='width:90%'><legend>所有的文档参数</legend><br/>"); ServletContext servletContext = this.getServletConfig().getServletContext(); String uploadFolder = servletContext.getInitParameter("upload folder");
String allowedFileType = servletContext.getInitParameter("allowed file type"); out.println("<div class='line'>");
out.println(" <div align='left' class='leftDiv'>上传文件夹</div>");
out.println(" <div align='left' class='rightDiv'>" + uploadFolder + "</div>");
out.println("</div>"); out.println("<div class='line'>");
out.println(" <div align='left' class='leftDiv'>实际磁盘路径</div>");
out.println(" <div align='left' class='rightDiv'>" + servletContext.getRealPath(uploadFolder) + "</div>");
out.println("</div>"); out.println("<div class='line'>");
out.println(" <div align='left' class='leftDiv'>允许上传的类型</div>");
out.println(" <div align='left' class='rightDiv'>" + allowedFileType + "</div>");
out.println("</div>"); out.println("</fieldset></div>"); out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
}
效果
3资源注射@Resource
不需要servlet主动去读取，tomcat启动时会把web.xml里配置的信息主动注射到servlet里。
只需要@Resource注解。
<env-entry>
<env-entry-name>hello</env-entry-name>
<env-entry-type>java.lang.String</env-entry-type>
<env-entry-value>
Hello, Welcome to the JavaEE Resource Injection.
</env-entry-value>
</env-entry> <env-entry>
<env-entry-name>i</env-entry-name>
<env-entry-type>java.lang.Integer</env-entry-type>
<env-entry-value>30</env-entry-value>
</env-entry> <env-entry>
<env-entry-name>persons</env-entry-name>
<env-entry-type>java.lang.String</env-entry-type>
<env-entry-value>
Helloween, Cobain, Roses, Axl,
</env-entry-value>
</env-entry>
servlet程序读取
package com.servlet; import java.io.IOException;
import java.io.PrintWriter; import javax.annotation.Resource;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; public class InjectionServlet extends HttpServlet{
private static final long serialVersionUID = -8526907492073769090L; // 注入的 字符串
private @Resource(name="hello") String hello;
// 注入的 整数
private @Resource(name="i") int i; // 注入更常见的写法
@Resource(name="persons")
private String persons; public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { response.setCharacterEncoding("UTF-8");
request.setCharacterEncoding("UTF-8"); response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println(" <HEAD><TITLE>资源注入</TITLE></HEAD>");
out.println("<style>body {font-size:12px; }</style>"); out.println("<b>注入的字符串</b>：<br/> - " + hello + "<br/>");
out.println("<b>注入的整数</b>：<br/> - " + i + "<br/>");
out.println("<b>注入的字符串数组</b>：<br/>"); for(String person : persons.split(",")){
out.println(" - " + person + "<br/>");
} out.println(" <BODY>");
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
}
效果