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张志宇 SERVELET JSP学习讲义-07_SERVLET为什么有2个init方法
package com.zzk.cn;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class TestInitServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.setContentType("text/html;charset=GBK");
PrintWriter out = resp.getWriter();
out.println(this.getServletConfig().getServletName());
// out.println(this.getServletConfig().getInitParameter("name"));
// java.util.Enumeration params = this.getServletConfig()
// .getInitParameterNames();
// for (; params.hasMoreElements();) {
// String name = params.nextElement().toString();
// String value = this.getServletConfig().getInitParameter(name);
// value = new String(value.getBytes("iso8859-1"),"GBK");
// out.println(value);
// }
out.close();
}
}
然后web.xml这么配置：
<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns="https://java.sun.com/xml/ns/javaee"
xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="https://java.sun.com/xml/ns/javaee
https://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
version="3.0"
metadata-complete="true">
<servlet>
<servlet-name>Myfirstservlet</servlet-name>
<servlet-class>com.zzk.cn.HelloWorldServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Myfirstservlet</servlet-name>
<url-pattern>/HelloWorldServlet</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>TestLifeCycleServlet</servlet-name>
<servlet-class>com.zzk.cn.TestLifeCycleServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>TestLifeCycleServlet</servlet-name>
<url-pattern>/TestLifeCycleServlet</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>TestInitServlet</servlet-name>
<servlet-class>com.zzk.cn.TestInitServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>TestInitServlet</servlet-name>
<url-pattern>/TestInitServlet</url-pattern>
</servlet-mapping>
</web-app>
运行tomcat，在tomcat页面中显示的是
TestInitServlet
这里输出的是
<servlet-name>TestInitServlet</servlet-name>
继续编辑
package com.zzk.cn;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class TestInitServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.setContentType("text/html;charset=GBK");
PrintWriter out = resp.getWriter();
out.println(this.getServletConfig().getServletName());
out.println(this.getServletConfig().getInitParameter("name"));
out.println(this.getServletConfig().getInitParameter("gender"));
// java.util.Enumeration params = this.getServletConfig()
// .getInitParameterNames();
// for (; params.hasMoreElements();) {
// String name = params.nextElement().toString();
// String value = this.getServletConfig().getInitParameter(name);
// value = new String(value.getBytes("iso8859-1"),"GBK");
// out.println(value);
// }
out.close();
}
}
web.xml修改为英文（中文有乱码问题）
<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns="https://java.sun.com/xml/ns/javaee"
xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="https://java.sun.com/xml/ns/javaee
https://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
version="3.0"
metadata-complete="true">
<servlet>
<servlet-name>Myfirstservlet</servlet-name>
<servlet-class>com.zzk.cn.HelloWorldServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Myfirstservlet</servlet-name>
<url-pattern>/HelloWorldServlet</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>TestLifeCycleServlet</servlet-name>
<servlet-class>com.zzk.cn.TestLifeCycleServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>TestLifeCycleServlet</servlet-name>
<url-pattern>/TestLifeCycleServlet</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>TestInitServlet</servlet-name>
<servlet-class>com.zzk.cn.TestInitServlet</servlet-class>
<init-param>
<param-name>name</param-name>
<param-value>Tom</param-value>
</init-param>
<init-param>
<param-name>gender</param-name>
<param-value>man</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>TestInitServlet</servlet-name>
<url-pattern>/TestInitServlet</url-pattern>
</servlet-mapping>
</web-app>
输出：
TestInitServlet Tom man
继续修改：循环输出：
package com.zzk.cn;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class TestInitServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.setContentType("text/html;charset=GBK");
PrintWriter out = resp.getWriter();
out.println(this.getServletConfig().getServletName());
out.println(this.getServletConfig().getInitParameter("name"));
out.println(this.getServletConfig().getInitParameter("gender"));
java.util.Enumeration params = this.getServletConfig()
.getInitParameterNames();
for (; params.hasMoreElements();) {
String name = params.nextElement().toString();
String value = this.getServletConfig().getInitParameter(name);
value = new String(value.getBytes("iso8859-1"),"GBK");
out.println(value);
}
out.close();
}
}
输出结果：
TestInitServlet Tom man Tom man
为什么拥有两个init()
³init(servletconfig config)
²this.config = config
²init();
²重写必须得super.init(config)
±不然不能使用this.getServletConfig
±当然也就不能用getInitParameter();
³我们只需要重写init();
防止程序员调用第一个，而忘记使用super
最后更新：2017-04-02 22:16:10