一、第一个Servlet
1、解压空站点，运行：http://localhost:8088/myweb/
2、编写Java文件：
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class HelloWorld extends HttpServlet
{
public void doGet(HttpServletRequest request,HttpServletResponse response)throws IOException, ServletException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<body bgcolor=\"white\">");
out.println("<head>");
out.println("<title>Hello!</title>");
out.println("</head>");
out.println("<body>");
out.println("Hello World!");
out.println("</body>");
out.println("</html>");
}
}
编译时需要<Tomcat>\common\lib下的包servlet-api.jar，如：
javac -classpath "C:\Program Files\Apache Software Foundation\Tomcat 5.0\common\lib\servlet-api.jar" HelloWorld.java
3、将class文件放入站点的WEB-INF\classes目录
4、修改web.xml文件（区分URL的大小写）：
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/j2ee/dtds/web-app_2_3.dtd">
<web-app>
<display-name></display-name>
<description></description>
<servlet>
<servlet-name>HelloWorld</servlet-name>
<servlet-class>HelloWorld</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HelloWorld</servlet-name>
<url-pattern>/hello</url-pattern>
</servlet-mapping>
</web-app>
5、运行：
http://localhost:8088/myweb/hello
（可能要重启tomcat）
说明：关于jar文件的存放
server\lib下的jar只能被tomcat访问使用
shared\lib下的jar只能被所有web应用程序访问使用
common\lib下的jar即可以被tomcat访问使用，也可以被所有web应用程序访问使用
应用程序的WEB-INF\lib下的jar只能被当前应用程序访问使用
6、问题：
1）修改web.xml文件为：
<servlet-mapping>
<servlet-name>HelloWorld</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
2）放入jsp-examples应用程序中运行之
二、使用Eclipse开发
三、基本使用
1、中文问题，修改doGet方法，如：
response.setContentType("text/html;charset=GBK");
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<body bgcolor=\"white\">");
out.println("<head>");
out.println("<title>你好！</title>");
out.println("</head>");
out.println("<body>");
out.println("欢迎来到Servlet！");
out.println("</body>");
out.println("</html>");
2、Post和Get提交
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class HelloWorld extends HttpServlet
{
public void doPost(HttpServletRequest request,HttpServletResponse response)throws IOException, ServletException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<html><body>Post</body></html>");
}
public void doGet(HttpServletRequest request,HttpServletResponse response)throws IOException, ServletException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<html><body>Get</body></html>");
}
}
直接通过浏览器键入：http://localhost:8088/lsq/HelloWorld
发现显示为：Get
但是通过下面的网页访问此servlet，却显示为：Post
<html>
<head>
</head>
<body>
<form method="POST" action="http://localhost:8088/lsq/HelloWorld">
<input type="submit" value="提交" name="B1">
</form>
</body>
</html>
更有意思的组合：
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
doGet(request, response);
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<html><body>Get</body></html>");
}
3、更加灵活的字符串输出
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class HelloWorld extends HttpServlet
{
public void doGet(HttpServletRequest request,HttpServletResponse response)throws IOException, ServletException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
StringBuffer buf = new StringBuffer();
buf.append("<html><body>Get</body></html>");
out.println( buf.toString() );
out.close();
}
}
4、显示时间
代码为：
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.Date;
public class HelloWorld extends HttpServlet
{
public void doGet(HttpServletRequest request,HttpServletResponse response)throws IOException, ServletException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
Date d=new Date();
StringBuffer buf = new StringBuffer();
buf.append(d.toString());
out.println( buf.toString() );
out.close();
}
}
5、参数的使用
参数分为post参数和get参数两种，都可以使用HttpServletRequest对象的getParameter()获取，此方法的参数即为servlet参数的名称，如：
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class HelloWorld extends HttpServlet
{
public void doPost(HttpServletRequest request,HttpServletResponse response)throws IOException, ServletException
{
String value=request.getParameter("postKey");
response.setContentType("text/html");
PrintWriter out=response.getWriter();
StringBuffer buf=new StringBuffer();
buf.append("<html><body>");
buf.append(value);
buf.append("</body></html>");
out.println(buf.toString());
out.close();
}
public void doGet(HttpServletRequest request,HttpServletResponse response)throws IOException, ServletException
{
String value=request.getParameter("getKey");
response.setContentType("text/html");
PrintWriter out=response.getWriter();
StringBuffer buf=new StringBuffer();
buf.append("<html><body>");
buf.append(value);
buf.append("</body></html>");
out.println(buf.toString());
out.close();
}
}
对于Post方式，访问网页为：
<HTML>
<HEAD>
</HEAD>
<BODY>
<FORM METHOD="POST" ACTION="http://localhost:8088/myweb/hello">
<input type="text" name="postKey" size="20"><INPUT TYPE=submit VALUE="提交">
</FORM>
</BODY>
</HTML>
对于get方式，访问方式为：
http://localhost:8088/myweb/hello?getKey=5656
注意汉字参数的处理：
String value=request.getParameter("getKey");
value = new String(value.getBytes("ISO-8859-1"), "GB2312");
response.setContentType("text/html;charset=GB2312");
6、使用集合遍历的方式得到所有的参数，如：
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 HelloWorld extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println(request.getQueryString() + "<p>");
Enumeration enumParam = request.getParameterNames();
while (enumParam.hasMoreElements()) {
String paramName = (String) enumParam.nextElement();
String paramValues[] = request.getParameterValues(paramName);
if (paramValues != null)
for (int i = 0; i < paramValues.length; i++)
out.println(paramName + " (" + i + "): " + paramValues[i]
+ "<p>");
}
}
}
直接运行http://localhost:8088/myweb/hello
得到结果
null
运行http://localhost:8088/myweb/hello?f=a&g=d
得到结果
f=a&g=d
g (0): d
f (0): a
运行http://localhost:8088/myweb/h
从零开始学习javaEE(从配置eclipse到第一个程序成功执行)
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2009-06-09
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