jdbc

*jdbc
先创建5包，分别为：
com.bdqn.dao(BaseDao.java DeptDao.java);
com.bdqn.dao.impl(DeptImp.java);
com.bdqn.entity(Dept.java);
com.bdqn.text(Text.java);测试包
com.bdqn.untils(Contants.java)

package com.bdqn.dao;import java.io.IOException;import java.io.InputStream;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;import java.util.Properties;import com.bdqn.utils.Contants;public class BaseDao {    private static Connection conn = null;    /*private static String driver; // 数据库驱动字符串    private static String url; // 连接URL字符串    private static String user; // 数据库用户名    private static String password; // 用户密码     */       static{ //在项目启动加载          System.out.println("哈哈哈");          init();      }    //初始化配置文件    public   static  void  init(){        try {            Properties properties  = new Properties();            //得到文件的路径            String fileName = "database.properties";            //文件加载到流里面            InputStream is = BaseDao.class.getClassLoader().getResourceAsStream(fileName);            //读取配置信息            properties.load(is);            Contants.driver=    properties.getProperty("driver");            Contants.url= properties.getProperty("url");            Contants.user=  properties.getProperty("user");            Contants.pwd=  properties.getProperty("password");        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }    //获取连接      public  static  Connection  getConnection(){        //加载驱动        try {            Class.forName(Contants.driver);            conn =  DriverManager.getConnection(Contants.url, Contants.user, Contants.pwd);        } catch (ClassNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (SQLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return conn;    }    //关闭资源    public   static void  close(Connection conn ,Statement st, ResultSet rs){        try {            if(rs !=null){                rs.close();            }            if(st !=null){                st.close();            }            if(conn !=null){                conn.close();            }        } catch (SQLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }    //增删改的方法    public    static int  update(String sql,Object[] objects){        int num=0;        PreparedStatement ps = null;        try {            conn  = getConnection();            ps =conn.prepareStatement(sql);            if(objects !=null && objects.length>0){                for (int i = 0; i < objects.length; i++) {                    ps.setObject((i+1),objects[i]);                }            }            num= ps.executeUpdate();        } catch (SQLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }finally{            close(conn, ps, null);        }        return num;    }       //查询    public  static  ResultSet getResultSet(String sql,Object[] objects){        PreparedStatement ps  = null;        ResultSet  rs = null;        try {            conn =  getConnection();            ps =   conn.prepareStatement(sql);            if(objects !=null && objects.length>0){                for (int i = 0; i < objects.length; i++) {                    ps.setObject((i+1), objects[i]);                }            }            rs= ps.executeQuery();        } catch (SQLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return rs;    }}

接口为以下：

package com.bdqn.dao;import java.util.List;import com.bdqn.entity.Dept;public interface DeptDao {    //增加    int insertDept(Dept dept);    //修改    int  updateDept(Dept dept);    //删除    int  deleteDept(int did);    //全查    List<Dept> selectAllDept();    //根据id查询    List<Dept> selectDept(int did);}

实现方法：

package com.bdqn.dao.impl;import java.sql.ResultSet;import java.sql.SQLException;import java.util.ArrayList;import java.util.List;import com.bdqn.dao.BaseDao;import com.bdqn.dao.DeptDao;import com.bdqn.entity.Dept;public class DeptImpl  extends BaseDao implements DeptDao {    @Override    public int insertDept(Dept dept) {        String sql = "insert into dept values(?,?,?,?)";        /*Dept dept2  = new Dept();*/        Object [] objects =  {dept.getDid(),dept.getDname(),dept.getDage(),dept.getDmesc()};        int num  =   this.update(sql, objects);        return num;    }    @Override    public int updateDept(Dept dept) {        String sql = "update  dept  set dname=? where did=?";        /*Dept dept2  = new Dept();*/        Object [] objects =  {dept.getDname(),dept.getDid()};        int num  =   this.update(sql, objects);        return num;    }    @Override    public int deleteDept(int did) {        String sql = "delete from dept where did=?";        /*Dept dept2  = new Dept();*/        Object [] objects =  {did};        int num  =   this.update(sql, objects);        return num;    }    @Override    public List<Dept> selectAllDept() {        String sql  = "select  * from dept";        List<Dept> list =null;        try {            ResultSet rs =   this.getResultSet(sql, null);            list = new ArrayList<Dept>();            while (rs.next()) {                Dept dept  = new Dept();              int did = rs.getInt("did");              String dname = rs.getString("dname");              int dage  = rs.getInt("dage");              String dmesc = rs.getString("dmesc");              dept.setDid(did);              dept.setDname(dname);              dept.setDage(dage);              dept.setDmesc(dmesc);              list.add(dept);            }        } catch (SQLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return list;    }    @Override    public List<Dept> selectDept(int did) {        String sql  = "select  * from dept where did=?";        List<Dept> list =null;         Object[] objects={did};        try {            ResultSet rs =   this.getResultSet(sql, objects);            list = new ArrayList<Dept>();            while (rs.next()) {                Dept dept  = new Dept();              int did1 = rs.getInt("did");              String dname = rs.getString("dname");              int dage  = rs.getInt("dage");              String dmesc = rs.getString("dmesc");              dept.setDid(did1);              dept.setDname(dname);              dept.setDage(dage);              dept.setDmesc(dmesc);              list.add(dept);            }        } catch (SQLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return list;    }}

在实体类进行封装

package com.bdqn.entity;import java.io.Serializable;public class Dept implements Serializable{    private  int did;    private  String dname;    private   int dage;    private   String dmesc;    public int getDid() {        return did;    }    public void setDid(int did) {        this.did = did;    }    public String getDname() {        return dname;    }    public void setDname(String dname) {        this.dname = dname;    }    public int getDage() {        return dage;    }    public void setDage(int dage) {        this.dage = dage;    }    public String getDmesc() {        return dmesc;    }    public void setDmesc(String dmesc) {        this.dmesc = dmesc;    }    public Dept(int did, String dname, int dage, String dmesc) {        this.did = did;        this.dname = dname;        this.dage = dage;        this.dmesc = dmesc;    }    public Dept() {    }    @Override    public String toString() {        return "Dept [did=" + did + ", dname=" + dname + ", dage=" + dage                + ", dmesc=" + dmesc + "]";    }}

服务类中存储配置信息

package com.bdqn.utils;public   class Contants {    public   static    String driver;    public   static   String url;    public   static    String  user;    public   static   String pwd;}

最后在测试类中测试

package com.bdqn.text;import java.util.List;import com.bdqn.dao.DeptDao;import com.bdqn.dao.impl.DeptImpl;import com.bdqn.entity.Dept;public class Text {    public static void main(String[] args) {        DeptDao dao  = new  DeptImpl();        /* Dept dept  = new Dept();          dept.setDname("aaa");          dept.setDid(10);*/        List<Dept> list =   dao.selectDept(2);        for(Dept dept  : list){            System.out.println(dept.toString());        }    }}

总结：对于jdbc链接数据库，思路大致明白，可是操作不一定能不看打出来，必须要多练，对于增删改查还有不熟悉的地方。