Java基础开发之JDBC操作数据库增删改查,分页查询实例详解

2020-02-19 20:01:47于海丽

调用jsonArray查询

public static void queryJsonArray(){
//   String sql = "select * from user u";
    String sql = "select u.*,d.* from user u,depart d where u.depart_id=d.id";
//   String sql = "select u.id AS uid,u.name,u.sex,u.depart_id AS departId,d.name from user u,depart d where u.depart_id=d.id";
//   String sql = "select u.id,u.name,u.sex,u.depart_id AS departId,d.* from user u,depart d where u.depart_id=d.id";
    try {
      JSONArray jsonArray = baseImp.queryForJsonArrayAttachTableName(2,2,sql, null);
//     JSONArray jsonArray = baseImp.queryForJsonArray(sql, null);
      System.out.println(jsonArray.toString());
      for (int i = 0; i < jsonArray.size(); i++) {
        JSONObject jsonObject = jsonArray.getJSONObject(i);
        Iterator<?> iterator = jsonObject.keys();
        Object key = null;
        while (iterator.hasNext()) {
          key = iterator.next();
          System.out.print(key+" "+jsonObject.get(key)+" ");
        }
        System.out.println();
      }
    } catch (SQLException e) {
      e.printStackTrace();
    }
  }

结果

[{"user.id":"4","user.name":"王五","user.sex":"0","user.depart_id":"3","depart.id":"3","depart.name":"研发部","depart.desc":"这是研发部"},{"user.id":"5","user.name":"赵六","user.sex":"1","user.depart_id":"1","depart.id":"1","depart.name":"测试部","depart.desc":"这是测试部"}]
user.id 4 user.name 王五 user.sex 0 user.depart_id 3 depart.id 3 depart.name 研发部 depart.desc 这是研发部 
user.id 5 user.name 赵六 user.sex 1 user.depart_id 1 depart.id 1 depart.name 测试部 depart.desc 这是测试部

3.查询总记录条数

/**
   * 查询记录条数
   * @param sql 例如:"select count(*) from user where xxx"
   * @param values
   * @throws SQLException 
   */
  public int queryCount(String sql,Object... values) throws SQLException{
    int count = -1;
    Connection conn = null;
    PreparedStatement pStmt = null;
    conn = this.getConnection(conn);
    pStmt = conn.prepareStatement(sql);
    //设置参数
    if(pStmt != null && values != null && values.length > 0){
      for (int i = 0; i < values.length; i++) {
        pStmt.setObject(i+1, values[i]);
      }
    }
    ResultSet rs = pStmt.executeQuery();
    if(rs != null){
      try {
        while(rs.next()){
          count = rs.getInt(1);
        }
      }finally{
        if(rs != null){
          rs.close();
        }
        if(pStmt != null){
          pStmt.close();
        }
        if (conn != null) {
          this.closeConnection(conn);
        }
      }
    }
    return count;
  }

调用查询总记录条数

public static void queryCount(){
    String sql = "select count(*) from user u";
    try {
      System.out.println("count="+baseImp.queryCount(sql, null));
    } catch (SQLException e) {
      e.printStackTrace();
    }
  }