Java EE WEB工程师培训-JDBC+Servlet+JSP整合开发之04.JDBC Resultset 推荐

• 本季内容提要
–ResultSet 简介
–Java 数据类型与SQL数据类型的映射
–ResultSet 常用方法
• next()
• getXXX()
–实例
• 从结果集中获得数据
##############Michael分割线###################
• ResultSet 简介
–用来获得SQL语句的查询结果
–结果集包含了SQL语句的查询结果数据
–调用语句的executeQuery方法返回结果集对象
• Java 数据类型与SQL数据类型的映射



• ResultSet 常用方法
–next()
• 返回boolean类型数据，用来判断结果集中是否有数据
–getXXX()
• 获得结果集中的数据项
–可以根据列名称
–可以根据列索引
• 实例
–从结果集中获得数据


#####################Michael分割线########################
Main.java

package com.michael.main;

import com.michael.jdbc.TestResultSet;

public class Main {

/**
* @param args
*/
public static void main(String[] args) {
/**
ConnectionUtil cu = new ConnectionUtil();
//第一种方法
System.out.println("第一种方法:"+cu.getConnection());
//第二种方法
System.out.println("第二种方法:"+cu.getConnection("com.mysql.jdbc.Driver","jdbc:mysql://localhost:3306/jdbc_db","root","mysqladmin"));
//第三种方法
System.out.println("第三种方法:"+cu.openConnection());
*/
TestResultSet.query();
}
}

TestResultSet.java

package com.michael.jdbc;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TestResultSet {
public static void query(){
Connection conn = new ConnectionUtil().openConnection();
try {
Statement stmt = conn.createStatement();
String sql = "select id,name,email from customertbl";
ResultSet rs = stmt.executeQuery(sql);
while(rs.next()){
int id = rs.getInt(1);
String name = rs.getString("name");
String email = rs.getString("email");
System.out.println(id+":"+name+":"+email);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
try {
conn.close();
} catch (SQLException e) {
conn = null;
e.printStackTrace();
}
}
}
}




#####################Michael分割线########################
在Servlet中我们要把后台查询结果显示在前台页面上，实现前后台的交互，我们可以把结果集封装到List中
Main.java

package com.michael.main;

import com.michael.jdbc.TestResultSet;

public class Main {

/**
* @param args
*/
public static void main(String[] args) {
/**
ConnectionUtil cu = new ConnectionUtil();
//第一种方法
System.out.println("第一种方法:"+cu.getConnection());
//第二种方法
System.out.println("第二种方法:"+cu.getConnection("com.mysql.jdbc.Driver","jdbc:mysql://localhost:3306/jdbc_db","root","mysqladmin"));
//第三种方法
System.out.println("第三种方法:"+cu.openConnection());
*/
TestResultSet.query();
}
}

ConnectionUtil.java

package com.michael.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.util.Properties;

public class ConnectionUtil {
//第一种方法
public Connection getConnection(){
Connection conn = null;
try {
//Class.forName加载驱动
Class.forName("com.mysql.jdbc.Driver");
//DriverManager获得连接
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbc_db","root","mysqladmin");
return conn;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
//第二种方法
public Connection getConnection(String driver,String url,String user,String password){
Connection conn = null;
try {
//Class.forName加载驱动
Class.forName(driver);
//DriverManager获得连接
conn = DriverManager.getConnection(url,user,password);
return conn;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
//第三种方法
public Connection openConnection(){
String driver = "";
String url = "";
String user = "";
String password = "";
Properties prop = new Properties();
Connection conn = null;
try {
//加载属性文件
prop.load(this.getClass().getClassLoader().getResourceAsStream("DBConfig.properties"));
driver = prop.getProperty("driver");
url = prop.getProperty("url");
user = prop.getProperty("user");
password = prop.getProperty("password");
//Class.forName加载驱动
Class.forName(driver);
//DriverManager获得连接
conn = DriverManager.getConnection(url,user,password);
return conn;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}

}

TestResultSet.java

package com.michael.jdbc;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

public class TestResultSet {
public static List query(){
Connection conn = new ConnectionUtil().openConnection();
try {
Statement stmt = conn.createStatement();
String sql = "select id,name,email from customertbl";
ResultSet rs = stmt.executeQuery(sql);
//将结果集封装到List中
List list = new ArrayList();
while(rs.next()){
// 可以根据列名称也可以根据列索引
int id = rs.getInt(1);
String name = rs.getString("name");
String email = rs.getString("email");
System.out.println(id+":"+name+":"+email);
Customer c = new Customer();
c.setId(id);
c.setName(name);
c.setEmail(email);
//将对象存放到list容器中
list.add(c);
}
return list;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
try {
conn.close();
} catch (SQLException e) {
conn = null;
e.printStackTrace();
}
}
return null;
}
}

Customer.java

package com.michael.jdbc;
//对象关系映射ORM
public class Customer {
private int id;
private String name;
private String email;
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}



#####################Michael分割线########################

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