java 使用策略模式操作JDBC数据库

java 使用策略模式操作jdbc数据库

1：构造一个操作数据库的工具类，可以获得连接和释放连接

public class dbutil { 
  private static connection conn = null; 
  static { //静态初始块 
      try { 
        class.forname("com.mysql.jdbc.driver"); 
        conn = drivermanager.getconnection("jdbc:mysql://127.0.0.1:3306/test", "root", "064319"); //初始化获取连接 
      } catch (classnotfoundexception e) { 
        e.printstacktrace(); 
      } catch (sqlexception e) { 
        e.printstacktrace(); 
      } 
  } 
 
  /** 
   * 释放连接 
   * @param rs 
   * @param psmt 
   * @param conn 
   * @throws sqlexception 
   */ 
  public static void closeall(resultset rs, preparedstatement psmt, connection conn) throws sqlexception { 
     
    if(rs != null) { 
      rs.close(); 
    }  
     
    if(psmt != null) { 
      psmt.close(); 
    } 
     
    if(conn != null) { 
      conn.close(); 
    } 
     
  } 
   
  /** 
   * 获取连接 
   * @return 
   */ 
  public static connection getconnection() { 
    return conn; 
  } 
   
  /** 
   * 根据表的名字来获得表的列信息 
   * @param tablename 
   */ 
  public static void gettablecolumninfobytablename(string tablename) { 
    connection conn = getconnection(); 
    resultset rs = null; 
    preparedstatement psmt = null; 
    string sql = "select * from " + tablename; 
    try { 
      psmt = conn.preparestatement(sql); 
      rs = psmt.executequery(); 
       
      resultsetmetadata resultsetmetadata = rs.getmetadata(); 
      for(int i = 1; i<= resultsetmetadata.getcolumncount(); i++) { 
        system.out.println(resultsetmetadata.getcolumnname(i)); 
      } 
       
    } catch (sqlexception e) { 
      e.printstacktrace(); 
    } finally { 
      try { 
        closeall(rs, psmt, conn); 
      } catch (sqlexception e) { 
        e.printstacktrace(); 
      } 
    } 
  } 
   
  /** 
   * 根据表的名字来获得表的信息 
   * @param tablename 
   */ 
  public static void gettableinfobytablename(string tablename) { 
    connection conn = getconnection(); 
    preparedstatement psmt = null; 
    resultset rs = null; 
    string sql = "select * from " + tablename; 
    try { 
      psmt = conn.preparestatement(sql); 
      rs = psmt.executequery(); 
       
      while(rs.next()) { 
        resultsetmetadata resultsetmetadata = rs.getmetadata(); 
        for(int i = 1; i<= resultsetmetadata.getcolumncount(); i++) { 
          if(i < resultsetmetadata.getcolumncount()) { 
            system.out.print(rs.getobject(resultsetmetadata.getcolumnname(i)) + ", "); 
          } else { 
            system.out.print(rs.getobject(resultsetmetadata.getcolumnname(i))); 
          } 
        } 
        system.out.println(); 
      } 
     
    } catch (sqlexception e) { 
      e.printstacktrace(); 
    } finally { 
      try { 
        closeall(rs, psmt, conn); 
      } catch (sqlexception e) { 
        e.printstacktrace(); 
      } 
    } 
  } 
} 

2：构造一个操作数据库的basedao类

public class basedao { 
   
  /** 
   * 根据一些参数来保存相应的对象 
   * @param sql 要执行的sql语句 
   * @param params 为sql语句中相应的参数赋值 
   * @return 
   */ 
  protected boolean saveorupdate(string sql, object[] params) { 
    connection conn = null; 
    preparedstatement psmt = null; 
    boolean flag = false; 
     
    conn = dbutil.getconnection(); 
    if(conn != null) { 
      try { 
        psmt = conn.preparestatement(sql); 
        for(int i = 1; i <= params.length; i++) { 
          psmt.setobject(i, params[i-1]); 
        } 
        if(psmt.executeupdate() > 0) { 
          flag = true; 
        } 
         
      } catch (sqlexception e) { 
        e.printstacktrace(); 
      } finally { 
        try { 
          dbutil.closeall(null, psmt, conn); 
        } catch (sqlexception e) { 
          e.printstacktrace(); 
        } 
      } 
    }  
    return flag; 
  } 
   
  /** 
   * 根据一定的参数获得某个具体的对象 
   * @param sql 要执行的sql语句 
   * @param params 为sql语句中相应的参数赋值 
   * @return 
   */ 
  public object queryforobject(string sql, object[] params, rowmapforobject rowmapforobject) { 
    connection conn = null; 
    preparedstatement psmt = null; 
     
    conn = dbutil.getconnection(); 
    object obj = null; 
    resultset rs = null; 
     
    if(conn != null) { 
      try { 
        psmt = conn.preparestatement(sql); 
        if(params != null && params.length > 0) { 
          for(int i = 1; i <= params.length; i++) { 
             psmt.setobject(i, params[i - 1]); 
          } 
        } 
        rs = psmt.executequery(); 
        obj = rowmapforobject.rowmapforobject(rs); 
         
      } catch (sqlexception e) { 
        e.printstacktrace(); 
      } finally { 
        try { 
          dbutil.closeall(null, psmt, conn); 
        } catch (sqlexception e) { 
          e.printstacktrace(); 
        } 
      } 
    } 
     
    return obj; 
  } 
 
   
  /** 
   * 根据相应的参数获得查询的结果集 
   * @param sql 
   * @param params 
   * @return 
   */ 
  public list queryforlist(string sql, object[] params, rowmapforlist rowmapforlist) { 
    connection conn = null; 
    preparedstatement psmt = null; 
     
    conn = dbutil.getconnection(); 
    list list = null; 
    resultset rs = null; 
     
    if(conn != null) { 
      try { 
        psmt = conn.preparestatement(sql); 
        if(params != null && params.length > 0) { 
          for(int i = 1; i <= params.length; i++) { 
             psmt.setobject(i, params[i - 1]); 
          } 
        } 
        rs = psmt.executequery(sql); 
        list = new arraylist(); 
        list = rowmapforlist.rowmapforlist(rs); 
         
      } catch (sqlexception e) { 
        e.printstacktrace(); 
      } finally { 
        try { 
          dbutil.closeall(null, psmt, conn); 
        } catch (sqlexception e) { 
          e.printstacktrace(); 
        } 
      } 
    } 
     
    return list; 
  } 
   
} 

3：新建一个studentdao类，该类继承自basedao，实现对student的管理

public class studentdao extends basedao { 
 
  /** 
   * 保存一个student的信息 
   */ 
  public boolean savestudent(student student) { 
    string sql = "insert into t_student(name, age) values(?, ?)"; 
    object[] params = new object[]{student.getname(), student.getage()}; 
    return super.saveorupdate(sql, params); 
  } 
   
  /** 
   * 根据id获得一个student的信息 
   * @param id 
   * @return 
   */ 
  public student getstudentbyid(long id) { 
    string sql = "select * from t_student where id=?"; 
    object[] params = new object[]{id}; 
    return (student)super.queryforobject(sql, params, new rowmapforobject() { 
       
      public object rowmapforobject(resultset rs) { 
        student student = null; 
         try { 
          if(rs != null && rs.next()) { 
             student = new student(); 
             student.setage(rs.getint(student.age)); 
             student.setid(rs.getlong(student.id)); 
             student.setname(rs.getstring(student.name)); 
           } 
        } catch (sqlexception e) { 
          e.printstacktrace(); 
        } 
         return student; 
      } 
    }); 
  } 
 
  /** 
   * 获得所有student的信息 
   * @return 
   */ 
  public list getstudentall() { 
    string sql = "select * from t_student"; 
    list list = super.queryforlist(sql, null, new rowmapforlist() { 
 
      @override 
      public list rowmapforlist(resultset rs) { 
        list list = null; 
        try { 
          if(rs != null) { 
            list = new arraylist(); 
            while(rs.next()) { 
              student student = new student(); 
              student.setid(rs.getlong("id")); 
              student.setage(rs.getint("age")); 
              student.setname(rs.getstring("name")); 
              list.add(student); 
            } 
          } 
        } catch(sqlexception e) { 
          e.printstacktrace(); 
        } 
        return list; 
      } 
    }); 
     
    return list; 
  }   
} 

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