Java——JDBC操作数据库，分页查询

原文地址：http://blog.csdn.net/sapce_fish/article/details/52764678

对数据库的操作无非就是增删改查，其中数查询操作最为复杂，所以将查询单独讲解，我这里用的Mysql数据库

• 增删改操作
• 分页查询操作
  1.查询结果以list返回
  2.查询结果以jsonArray返回
  3.查询总记录条数

demo下载地址：http://download.csdn.net/detail/sapce_fish/9648391

先看一下相关的配置信息

public static final String USER_NAME = "root";

public static final String PWD = "123456789";

public static final String DRIVER = "com.mysql.jdbc.Driver";

public static final String URL = "jdbc:mysql://localhost:3306/web_demon";

/** 分页查询默认每页记录条数 */
public static final int PAGE_SIZE_DEFAULT = 10;

增删改操作

获取数据库连接对象

/**
     * 获取数据库连接
     * @return 数据库连接对象
     */
    public Connection getConnection(Connection conn) {
        if(conn == null){
            try {
                Class.forName(Config.DRIVER);
                conn = DriverManager.getConnection(Config.URL, Config.USER_NAME, Config.PWD);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return conn;
    }

封装增删改操作

/**
     * 新增，删除，插入操作
     * @param sql 执行的sql语句
     *           例如：新增语句  "insert into user (name,sex) values (?,?)";
     *              删除语句   "delete from user where id=?";
     *              修改语句   "update user set name=?,sex=? where id=? and sex=?";
     * @param values 对应的参数值
     * @return 影响条数，-1为异常
     */
    private int execute(String sql,Object... values){
        Connection conn = null;
        PreparedStatement pStmt = null;
        try {
            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]);
                }
            }
            int i =pStmt.executeUpdate();
            return i;
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (conn != null) {
                this.closeConnection(conn);
            }
        }
        return -1;
    }

调用方法

//新增
public static void insert(){
        String sql = "insert into user (name,sex) values (?,?)";
        Object[] values = new Object[]{"李四",0};
        int res = baseImp.execute(sql, values);
        System.out.println("insert res="+res);
    }

//删除
public static void delete(){
        String sql = "delete from user where id=?";
        Object[] values = new Object[]{2};
        int res = baseImp.execute(sql, values);
        System.out.println("delete res="+res);
    }

//更新
public static void update(){
        String sql = "update user set name=?,sex=? where id=? and sex=?";
        Object[] values = new Object[]{"张三",1,1,0};
        int res = baseImp.execute(sql, values);
        System.out.println("update res="+res);
    }

查询操作

1.查询结果以list返回

/**
     * 查询结果以list返回
     * @param pageIndex 页数
     * @param pageSize 每页记录条数
     * @param attachTableName 在结果集中是否给key值附加表名，例如：user.id,与id
     * @param sql 查询语句 例如："select u.id,u.name,u.sex,u.depart_id AS departId,d.* from user u,depart d where u.depart_id=d.id"
     * @param values
     * @throws SQLException 
     */
    private List> queryList(int pageIndex,int pageSize,boolean attachTableName,String sql,Object... values) throws SQLException{
        Connection conn = null;
        PreparedStatement pStmt = null;
        List> dataList = null;
        //校验参数
        if(pageIndex <= 0){
            pageIndex = 1;
        }
        if(pageSize <= 0){
            pageSize = Config.PAGE_SIZE_DEFAULT;
        }
        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]);
            }
        }
        //设置最大查询到第几条记录
        pStmt.setMaxRows(pageIndex*pageSize);
        ResultSet rs = pStmt.executeQuery();
        //游标移动到要输出的第一条记录
        rs.relative((pageIndex-1)*pageSize);
        if(rs != null){
            try {
                dataList = new ArrayList>();
                ResultSetMetaData md = rs.getMetaData(); //得到结果集(rs)的结构信息，比如字段数、字段名等  
                //遍历结果集
                while(rs.next()){
                    Map map = new LinkedHashMap();
                    for (int i = 1; i <= md.getColumnCount(); i++) {
                        map.put(attachTableName?(formatTableName(md.getTableName(i))+"."+md.getColumnLabel(i)):(md.getColumnLabel(i)), rs.getObject(i));
                    }
                    dataList.add(map);
                }
            }finally{
                if(rs != null){
                    rs.close();
                }
                if(pStmt != null){
                    pStmt.close();
                }
                if (conn != null) {
                    this.closeConnection(conn);
                }
            }
        }
        return dataList;
    }

调用list查询

public static void queryList(){
        String sql = "select u.*,d.* from user u,depart d where u.depart_id=d.id";
        try {
            List> dataList = baseImp.queryForListAttachTableName(2,2,sql, null);
//          List> dataList = baseImp.queryForList(2,2,sql, null);
            for (Map map : dataList) {
                for (String key : map.keySet()) {
                    System.out.print(key+"="+map.get(key)+" ");
                }
                System.out.println();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

结果

2.查询结果以jsonArray返回

/**
     * 查询结果以ArrayList返回
     * @param 在结果集中是否给key值附加表名，例如：user.id,与id
     * @param sql 查询语句 例如："select u.id,u.name,u.sex,u.depart_id AS departId,d.* from user u,depart d where u.depart_id=d.id"
     * @param values
     * @throws SQLException 
     */
    private JSONArray queryJsonArray(int pageIndex,int pageSize,boolean attachTableName,String sql,Object... values) throws SQLException{
        JSONArray jsonArray = null;
        Connection conn = null;
        PreparedStatement pStmt = null;
        //校验参数
        if(pageIndex <= 0){
            pageIndex = 1;
        }
        if(pageSize <= 0){
            pageSize = Config.PAGE_SIZE_DEFAULT;
        }
        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]);
            }
        }
        //设置最大查询到第几条记录
        pStmt.setMaxRows(pageIndex*pageSize);
        ResultSet rs = pStmt.executeQuery();
        //游标移动到要输出的第一条记录
        rs.relative((pageIndex-1)*pageSize);
        if(rs != null){
            try {
                jsonArray = new JSONArray();
                ResultSetMetaData md = rs.getMetaData(); //得到结果集(rs)的结构信息，比如字段数、字段名等  
                //遍历结果集
                while(rs.next()){
                    JSONObject jsonObject = new JSONObject();
                    for (int i = 1; i <= md.getColumnCount(); i++) {
                        jsonObject.put(attachTableName?(formatTableName(md.getTableName(i))+"."+md.getColumnLabel(i)):(md.getColumnLabel(i)), rs.getObject(i)+"");
                    }
                    jsonArray.add(jsonObject);
                }
                }finally{
                    if(rs != null){
                        rs.close();
                    }
                    if(pStmt != null){
                        pStmt.close();
                    }
                    if (conn != null) {
                        this.closeConnection(conn);
                    }
                }
        }
        return jsonArray;
    }

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();
        }
    }

结果

至此已经介绍了JDBC操作数据库增删改查
如果有不明白的地方可以留言。有写错或者不好的地方欢迎指正