数据库预处理方法

---

title: 数据库预处理方法
tag: [数据库,java]
categories: 数据库

package useJDBC;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;


public class DAO {
//有关数据库使用的类
	protected static String dbClassName = "com.microsoft.sqlserver.jdbc.SQLServerDriver";
	protected static String dbUrl = "jdbc:sqlserver://localhost:1433;"//java连接sqlServer数据库的方法
			+ "DatabaseName=test;";
	protected static String dbUser = "sa";
	protected static String dbPwd = "123456";
	private static Connection conn = null;

	private DAO() {// 获得数据库连接
		try {
			if (conn == null) {
				Class.forName(dbClassName).newInstance();
				conn = DriverManager.getConnection(dbUrl, dbUser, dbPwd);
			} else
				return;
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
//数据库预处理：事先不知道有多少个参数，具体的调用方法看后面
	static ResultSet executeQuery(String sql,Object... objects ) {// 执行查询操作
		try {
			if (conn == null) new DAO();
			PreparedStatement ps = conn.prepareStatement(sql);//预处理
			if(objects !=null && objects.length>0){
				for(int i=0;i<objects.length;i++){
					ps.setObject(i+1, objects[i]);
				}
			}
			return ps.executeQuery();
		} catch (SQLException e) {
			e.printStackTrace();
			return null;
		}
	}

	static int executeUpdate(String sql, Object... objects) {// 执行其他操作

		try {
			if (conn == null)
				new DAO();
			PreparedStatement ps = conn.prepareStatement(sql);
			if(objects !=null && objects.length>0){
				for(int i=0;i<objects.length;i++){
					ps.setObject(i+1, objects[i]);
				}
			}
			return ps.executeUpdate();
		} catch (SQLException e) {
			e.printStackTrace();
			return -1;
		}
	}

	public static void close() {// 关闭连接
		try {
			conn.close();
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			conn = null;
		}
	}
}

下面是学生类进行操作

package useJDBC;

import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

public class StudentDAO {

	// 查询学生信息
	public static List<Student> getStudents() {
		List<Student> list = new ArrayList<Student>();
		String sql = "select * from student";
		ResultSet rs = DAO.executeQuery(sql);
		try {
			while (rs.next()) {
				Student student = new Student();
				student.setSno(rs.getString("sno"));
				// 或user.setSno(rs.getString(1));
				student.setSname(rs.getString("sname"));
				student.setSex(rs.getString("sex"));
				student.setAge(rs.getInt("age"));
				student.setClassId(rs.getInt("class"));
				list.add(student);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		DAO.close();
		return list;
	}

	// 删除学生信息
	public static int deleteStudent(Student student) {
		int i = 0;
		try {
			String sql = "delete from student where sno=?";//位置参数用？代替
			i = DAO.executeUpdate(sql,student.getSno());//这里调用的时候sql中有几个？就得有多少个参数
		} catch (Exception e) {
			e.printStackTrace();
		}
		DAO.close();
		return i;
	}

	// 添加学生信息
	public static int addStudent(Student student) {
		int i = 0;
		try {
			//待执行的sql语句
			String sql = "insert into student(sno,sname,sex,age,class) values(?,?,?,?,?)";
			
			//设置参数
			Object[] objs = new Object[5];
			objs[0] = student.getSno();
			objs[1] = student.getSname();
			objs[2] = student.getSex();
			objs[3] = student.getAge();
			objs[4] = student.getClassId();
		
			//调用通用方法执行SQL语句
			//注意
			//注意
			//注意
			//注意
			
			i = DAO.executeUpdate(sql,objs);
		} catch (Exception e) {
			e.printStackTrace();
		}
		DAO.close();
		return i;
	}

	// 修改学生信息
	public static int updateStudent(Student student) {
		int i = 0;
		try {
			//待执行的sql语句
			String sql = "update student set sname=?,sex=?,age=?,class=? where sno=?";
			
			//设置参数
			Object[] objs = new Object[5];
			objs[0] = student.getSname();
			objs[1] = student.getSex();
			objs[2] = student.getAge();
			objs[3] = student.getClassId();
			objs[4] = student.getSno();
			
			i = DAO.executeUpdate(sql,objs);
		} catch (Exception e) {
			e.printStackTrace();
		}
		DAO.close();
		return i;
	}
}