学习javaweb遇到了一些坑，一些问题总结下来，记个笔记。
学习servlet遇到的一些坑:
servlet实现用户登陆遇到的坑解决办法:
https://www.cnblogs.com/swxj/archive/2013/06/05/3119206.html
打开配置选择server runtime envir-->绑定运行环境
tomcat创建要自定义值
导入tomcat自带的jar包：项目右键--->build path-->add library-->选择Server Runtime--->选择tomcat服务器，这样就能自动导入所有tomcat下的jar包了！无需再二次导入。
使用Servlet简单实现用户登陆功能
除了这些jar包另外还需要二次导入jar包:c3p0-* jar包+commons-dbutils-*jar包
首先创建一张表用于测试用户登陆:
User表:
/*Mysql数据库*/
create table user(
username varchar(20),
password varchar(30),
id int
);
创建设置公共的servlet模块
1.套servlet模块直接调用模块
配置servlet加载项
eclipse里面搜索templates 找到java-->editor--->templates然后new
公共的模块代码:
设置模块名称servlet,创建servlet之后直接ser+alt+/自动补全就会全部代码结构就位。
package ${enclosing_package};
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ${primary_type_name} extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.getWriter().write("hello world!");
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
因为用到c3p0jar包所以固定模式下的c3p0-config.xml
<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config> <default-config>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql://127.0.0.1/数据库名</property>
<property name="user">数据库名</property>
<property name="password">数据库密码</property>
<property name="initialPoolSize">5</property>
<property name="maxPoolSize">20</property>
</default-config> <named-config name="test">
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql://127.0.0.1/数据库名</property>
<property name="user">数据库用户名</property>
<property name="password">数据库密码</property>
</named-config> </c3p0-config>
用到commons-dbutils-*jar包，需要一个数据库dbutilsl类
创建包名:cn.test.utils,文件名:DataSourceUtils.java
内容如下:
package cn.test.utils; import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement; import javax.sql.DataSource; import com.mchange.v2.c3p0.ComboPooledDataSource; public class DataSourceUtils { private static DataSource dataSource = new ComboPooledDataSource(); private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>(); // 直接可以获取一个连接池
public static DataSource getDataSource() {
return dataSource;
} // 获取连接对象
public static Connection getConnection() throws SQLException { Connection con = tl.get();
if (con == null) {
con = dataSource.getConnection();
tl.set(con);
}
return con;
} // 开启事务
public static void startTransaction() throws SQLException {
Connection con = getConnection();
if (con != null) {
con.setAutoCommit(false);
}
} // 事务回滚
public static void rollback() throws SQLException {
Connection con = getConnection();
if (con != null) {
con.rollback();
}
} // 提交并且 关闭资源及从ThreadLocall中释放
public static void commitAndRelease() throws SQLException {
Connection con = getConnection();
if (con != null) {
con.commit(); // 事务提交
con.close();// 关闭资源
tl.remove();// 从线程绑定中移除
}
} // 关闭资源方法
public static void closeConnection() throws SQLException {
Connection con = getConnection();
if (con != null) {
con.close();
}
} public static void closeStatement(Statement st) throws SQLException {
if (st != null) {
st.close();
}
} public static void closeResultSet(ResultSet rs) throws SQLException {
if (rs != null) {
rs.close();
}
} }
创建User的用户类: cn.test.domain->User.java
package cn.test.domain;
//创建一个信息类
public class User {
private String username;
private String password;
private int id;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@Override
public String toString() {
return "User [username=" + username + ", password=" + password + ", id=" + id + "]";
} }
创建需要登陆的表单html视图页面:WebContent-->login.html
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="/TestPro/login" method="post">
账号:<input type="text" name="username"><br/>
密码:<input type="password" name="password"><br/>
<input type="submit" value="登陆">
</form>
</body>
</html>
设置我们的login servlet路径
cn.test.loginServlet--->LoginServlet.java 设置访问路径是login
package cn.test.loginServlet; import java.io.IOException;
import java.sql.SQLException; import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import com.mchange.*;
import cn.test.domain.User;
import cn.test.utils.DataSourceUtils; public class LoginServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String username = request.getParameter("username");
String password = request.getParameter("password"); QueryRunner queryRunner = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "select * from user where username=? and password=?";
User user = null;
try {
user = queryRunner.query(sql, new BeanHandler<User>(User.class), username, password);
// System.out.println(user);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} if (user != null) {
response.getWriter().write(user.toString());
} else {
response.getWriter().write("sorry you username or password is Error!");
}
} public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
访问http://localhost:对应端口/项目名称/login.html即可进行测试!