01_11_SERVLET中使用javabean
1. javabean
广义javabean = 普通java类
狭义javabean = 符合 Sun JavaBean标准的类
在Servlet中使用Bean和在通常程序中使用Bean类似
属性名称第一个字母必须小写，一般private，
比如，private productId
一般具有getters and setters
要具有一个参数为空的构造方法
但Bean不应具有GUI表现
一般是用来实现某一业务逻辑或取得特定结果
2. 示例
2.1封装的javabean类
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class DB {
public static Connection getConn () {
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/world?user=root&password=123456");
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
}
public static Statement getStatement(Connection conn) {
Statement stmt = null;
if (conn != null) {
try {
stmt = conn.createStatement();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return stmt;
}
public static ResultSet getResultSet(Statement stmt, String sql) {
ResultSet rs = null;
if (stmt != null && sql != "") {
try {
rs = stmt.executeQuery(sql);
} catch (SQLException e) {
e.printStackTrace();
}
}
return rs;
}
public static void closeStmt(Statement stmt) {
if (stmt != null) {
try {
stmt.close();
stmt = null;
} catch (SQLException e) {
e.printStackTrace();
}
}
}
public static void closeConn(Connection conn) {
if (conn != null) {
try {
conn.close();
conn = null;
} catch (SQLException e) {
e.printStackTrace();
}
}
}
public static void closeRs(ResultSet rs) {
if (rs != null) {
try {
rs.close();
rs = null;
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
2.2展示
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println("<HEAD><TITLE>Servlet连接MySQL数据库</TITLE></HEAD>");
out.println("<BODY>");
out.print("<table align=\"center\" border=\"1\"><tr align=\"center\"><td>查询world库中city表中的Name列信息</td></tr>");
try {
conn = DB.getConn();
stmt = DB.getStatement(conn);
rs = DB.getResultSet(stmt, "select * from city");
while (rs.next()) {
out.println("<tr align=\"center\"><td>" +rs.getString("name") + "</td></tr>");
}
out.println("</table>");
} catch (SQLException e) {
e.printStackTrace();
} finally {
if (rs != null) {
try {
rs.close();
rs = null;
} catch (SQLException e) {
e.printStackTrace();
}
}
if (stmt != null) {
try {
stmt.close();
stmt = null;
} catch (SQLException e) {
e.printStackTrace();
}
}
if (conn != null) {
try {
conn.close();
conn = null;
} catch (SQLException e) {
e.printStackTrace();
}
}
}
out.println("</BODY>");
out.println("</HTML>");
out.flush();
out.close();
}