JDBC中execute、executeQuery和executeUpdate的区别

1.executeQuery
用于产生单个结果集（ResultSet）的语句，例如 SELECT 语句。 被使用最多的执行 SQL 语句的方法。这个方法被用来执行 SELECT 语句，它几乎是使用最多的 SQL 语句。但也只能执行查询语句，执行后返回代表查询结果的ResultSet对象。
2.executeUpdate
用于执行 INSERT、UPDATE 或 DELETE 语句以及 SQL DDL（数据定义语言）语句，例如 CREATE TABLE 和 DROP TABLE。INSERT、UPDATE 或 DELETE 语句的效果是修改表中零行或多行中的一列或多列。executeUpdate 的返回值是一个整数（int），指示受影响的行数（即更新计数）。对于 CREATE TABLE 或 DROP TABLE 等不操作行的语句，executeUpdate 的返回值总为零。
3.execute
可用于执行任何SQL语句，返回一个boolean值，表明执行该SQL语句是否返回了ResultSet。如果执行后第一个结果是ResultSet，则返回true，否则返回false。但它执行SQL语句时比较麻烦，通常我们没有必要使用execute方法来执行SQL语句，而是使用executeQuery或executeUpdate更适合，但如果在不清楚SQL语句的类型时则只能使用execute方法来执行该SQL语句了。

		//加载驱动
        Class.forName(driver);
        //获取数据库连接
        conn = DriverManager.getConnection(url, user, pass);
        //使用Connection来创建一个Statment对象
        stmt = conn.createStatement();
        //执行SQL,返回boolean值表示是否包含ResultSet
        boolean hasResultSet = stmt.execute(sql);
        //如果执行后有ResultSet结果集
        if (hasResultSet) {
            //获取结果集
            rs = stmt.getResultSet();
            //ResultSetMetaData是用于分析结果集的元数据接口
            ResultSetMetaData rsmd = rs.getMetaData();
            int columnCount = rsmd.getColumnCount();
            //迭代输出ResultSet对象
            while (rs.next()) {//依次输出每列的值
                for (int i = 0; i < columnCount; i++) {
                    System.out.print(rs.getString(i + 1) + "/t");
                }
                System.out.print("/n");
            }
        } else {
            System.out.println("该SQL语句影响的记录有" + stmt.getUpdateCount() + "条");
        }

4.MySqlUtil工具类

public class MySqlUtil {

    public static PreparedStatement ps;

    public static Connection conn;

    //openConnection是连接数据库
    public static Connection openConnection(String url, String user,
                                            String password) {
        try {
            final String DRIVER_NAME = "com.mysql.jdbc.Driver";
            Class.forName(DRIVER_NAME);
            conn = DriverManager.getConnection(url, user, password);
        } catch (ClassNotFoundException e) {
            conn = null;
        } catch (SQLException e) {
            conn = null;
            printLog(e);
        }
        return conn;
    }

    //查询数据库
    public static UgHouseBean queryUgHouse(String sql) {
        if (conn == null) {
            return null;
        }

        Statement statement = null;
        ResultSet result = null;
        UgHouseBean houseBean = null;
        try {
            statement = conn.createStatement();
            result = statement.executeQuery(sql);
            if (result != null && result.first()) {
                int idColumnIndex = result.findColumn("id");
                int user_noColumnIndex = result.findColumn("face_user_no");
                int stateColumnIndex = result.findColumn("state");
                int face_stateColumnIndex = result.findColumn("face_state");
                int user_idColumnInde = result.findColumn("user_id");
                int pad_stateColumnIndex = result.findColumn("pad_state");
                int door_stateColumnIndex = result.findColumn("door_state");
                while (!result.isAfterLast()) {
                    houseBean = new UgHouseBean();
                    houseBean.setId(result.getString(idColumnIndex));
                    houseBean.setFace_user_no(result.getString(user_noColumnIndex));
                    houseBean.setState(result.getString(stateColumnIndex));
                    houseBean.setFace_state(result.getString(face_stateColumnIndex));
                    houseBean.setUser_id(result.getString(user_idColumnInde));
                    houseBean.setDoor_state(result.getString(door_stateColumnIndex));
                    houseBean.setPad_state(result.getString(pad_stateColumnIndex));
                    // Logger.i(houseBean.toString());
                    result.next();
                }
            }
            return houseBean;
        } catch (SQLException e) {
            e.printStackTrace();
            printLog(e);
            Logger.i("查询数据库失败");
        } finally {
            try {
                if (result != null) {
                    result.close();
                    result = null;
                }
                if (statement != null) {
                    statement.close();
                    statement = null;
                }

            } catch (SQLException e) {
                e.printStackTrace();
                printLog(e);
            }
        }
        return houseBean;
    }

    //执行MySQL语句的函数
    public static boolean execSQL(String sql) {
        boolean execResult = false;
        if (conn == null) {
            return execResult;
        }

        Statement statement = null;

        try {
            statement = conn.createStatement();
            if (statement != null) {
                execResult = statement.execute(sql);
            }
        } catch (SQLException e) {
            execResult = false;
            e.printStackTrace();
            printLog(e);
        } finally {
            try {
                if (statement != null) {
                    statement.close();
                    statement = null;
                }
            } catch (SQLException e) {
                e.printStackTrace();
                printLog(e);
            }
        }

        return execResult;
    }

    public static boolean execSQLUpdate(String sql) {
        boolean execResult = false;
        if (conn == null) {
            return execResult;
        }

        Statement statement = null;
        try {
            statement = conn.createStatement();
            //该方法用于修改数据库内容的。
            if (statement != null) {
                int row = statement.executeUpdate(sql);
                if (row > 0) {
                    execResult = true;
                }
            }
        } catch (SQLException e) {
            execResult = false;
            e.printStackTrace();
            printLog(e);
        } finally {
            try {
                if (statement != null) {
                    statement.close();
                    statement = null;
                }
            } catch (SQLException e) {
                e.printStackTrace();
                printLog(e);
            }
        }
        return execResult;
    }

    /**
     * 创建用户组
     *
     * @param group
     * @return
     */
    public static boolean addGroup(Group group) {
        boolean execResult = false;
        if (conn == null) {
            return execResult;
        }
        PreparedStatement ps = null;
        try {
            ps = conn.prepareStatement("insert into user_group (group_id,ctime,update_time) values (?,?,?)");
            if (ps != null) {
                ps.setString(1, group.getGroupId());
                ps.setLong(2, System.currentTimeMillis());
                ps.setLong(3, System.currentTimeMillis());
                ps.executeUpdate();
                execResult = true;
            }
        } catch (SQLException e) {
            execResult = false;
            e.printStackTrace();
            printLog(e);
        } finally {
            try {
                if (ps != null) {
                    ps.close();
                    ps = null;
                }
            } catch (SQLException e) {
                e.printStackTrace();
                printLog(e);
            }
        }
        return execResult;
    }

    /**
     * 添加用户
     *
     * @return
     */
    public static boolean addUser(User user) {
        boolean execResult = false;
        if (conn == null) {
            return execResult;
        }
        PreparedStatement ps = null;
        try {
            ps = conn.prepareStatement("insert into ug_feature_user (user_id,face_user_no,user_info,group_id,ctime,update_time,door_id) values (?,?,?,?,?,?,?)");
            if (ps != null) {
                ps.setString(1, user.getUserId());
                ps.setString(2, user.getFace_user_no());
                ps.setString(3, user.getUserInfo());
                ps.setString(4, user.getGroupId());
                ps.setLong(5, System.currentTimeMillis());
                ps.setLong(6, System.currentTimeMillis());
                ps.setInt(7, user.getDoorId());
                ps.executeUpdate();

                for (Feature feature : user.getFeatureList()) {
                    execResult = addFeature(feature);
                }
            }
            EventBus.getDefault().post("In:添加新用户-" + user.getUserId());
        } catch (SQLException e) {
            execResult = false;
            e.printStackTrace();
            printLog(e);
            EventBus.getDefault().post("In:添加新用户失败-" + user.getUserId());
        } finally {
            try {
                if (ps != null) {
                    ps.close();
                    ps = null;
                }
            } catch (SQLException e) {
                e.printStackTrace();
                printLog(e);
                EventBus.getDefault().post("In:添加新用户失败-" + user.getUserId());
            }
        }
        return execResult;
    }

    /**
     * 添加人脸特征
     *
     * @param feature
     * @return
     */
    public static boolean addFeature(Feature feature) {
        boolean execResult = false;
        if (conn == null) {
            return execResult;
        }
        PreparedStatement ps = null;
        try {
            ps = conn.prepareStatement("insert into ug_feature (face_token,group_id,user_id,feature,image_name,ctime,update_time) values (?,?,?,?,?,?,?)");
            if (ps != null) {
                ps.setString(1, feature.getFaceToken());
                ps.setString(2, feature.getGroupId());
                ps.setString(3, feature.getUserId());
                ps.setBytes(4, feature.getFeature());
                ps.setString(5, feature.getImageName());
                ps.setLong(6, System.currentTimeMillis());
                ps.setLong(7, System.currentTimeMillis());
                ps.executeUpdate();
                execResult = true;
            }
        } catch (SQLException e) {
            execResult = false;
            e.printStackTrace();
            printLog(e);
        } finally {
            try {
                if (ps != null) {
                    ps.close();
                    ps = null;
                }
            } catch (SQLException e) {
                e.printStackTrace();
                printLog(e);
            }
        }
        return execResult;
    }

    /**
     * 查询用户
     *
     * @param groupId
     * @param userId
     * @return
     */
    public static User queryUser(String groupId, String userId) {
        if (conn == null) {
            return null;
        }
        PreparedStatement ps = null;
        User user = null;
        try {
            ps = conn.prepareStatement("select * from ug_feature_user where group_id='" + groupId + "' and user_id='" + userId + "';");
            if (ps != null) {
                ResultSet rs = ps.executeQuery();
                while (rs.next()) {
                    user = new User();
                    user.setDoorId(rs.getInt("door_id"));
                    user.setFace_user_no(rs.getString("face_user_no"));
                    user.setGroupId(rs.getString("group_id"));
                    user.setUserId(rs.getString("user_id"));
                    user.setUserInfo(rs.getString("user_info"));
                    user.setCtime(rs.getLong("ctime"));
                    user.setUpdateTime(rs.getLong("update_time"));
                }
            }
        } catch (SQLException e) {
            e.printStackTrace();
            printLog(e);
        } finally {
            try {
                if (ps != null) {
                    ps.close();
                    ps = null;
                }
            } catch (SQLException e) {
                e.printStackTrace();
                printLog(e);
            }
        }
        return user;
    }

    /**
     * 获取指定用户的人脸特征
     *
     * @param groupId
     * @param userId
     * @return
     */
    public static List queryFeature(String groupId, String userId) {
        if (conn == null) {
            return null;
        }
        ArrayList featureList = new ArrayList<>();
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            ps = conn.prepareStatement("select * from ug_feature where group_id='" + groupId + "' and user_id='" + userId + "';");
            if (ps != null) {
                rs = ps.executeQuery();
                while (rs.next()) {
                    Feature feature = new Feature();
                    feature.setGroupId(rs.getString("group_id"));
                    feature.setUserId(rs.getString("user_id"));
                    feature.setFaceToken(rs.getString("face_token"));
                    feature.setFeature(rs.getBytes("feature"));
                    feature.setImageName(rs.getString("image_name"));
                    feature.setCtime(rs.getLong("ctime"));
                    feature.setUpdateTime(rs.getLong("update_time"));
                    featureList.add(feature);
                }
            }
        } catch (SQLException e) {
            e.printStackTrace();
            printLog(e);
        } finally {
            try {
                if (rs != null) {
                    rs.close();
                    rs = null;
                }
                if (ps != null) {
                    ps.close();
                    ps = null;
                }
            } catch (SQLException e) {
                e.printStackTrace();
                printLog(e);
            }
        }
        return featureList;
    }

    /**
     * 查询指定组下面的所有人脸特征
     *
     * @param groupId
     * @return
     */
    public static List queryFeatureByGroupId(String groupId) {
        if (conn == null) {
            return null;
        }
        ArrayList featureList = new ArrayList<>();
        PreparedStatement ps = null;
        ResultSet rs = null;
        User user = null;
        try {
            ps = conn.prepareStatement("select * from ug_feature where group_id='" + groupId + "';");
            if (ps != null) {
                rs = ps.executeQuery();
                while (rs.next()) {
                    Feature feature = new Feature();
                    feature.setGroupId(rs.getString("group_id"));
                    feature.setUserId(rs.getString("user_id"));
                    feature.setFaceToken(rs.getString("face_token"));
                    feature.setFeature(rs.getBytes("feature"));
                    feature.setImageName(rs.getString("image_name"));
                    feature.setCtime(rs.getLong("ctime"));
                    feature.setUpdateTime(rs.getLong("update_time"));
                    featureList.add(feature);
                }
            }
        } catch (SQLException e) {
            e.printStackTrace();
            printLog(e);
        } finally {
            try {
                if (rs != null) {
                    rs.close();
                    rs = null;
                }
                if (ps != null) {
                    ps.close();
                    ps = null;
                }
            } catch (SQLException e) {
                e.printStackTrace();
                printLog(e);
            }
        }
        return featureList;
    }

    /**
     * 将指定路径的文件(比如：图片，word文档等)存储到数据库
     *
     * @param strFile 要存放到数据库的文件路径，如D:\\a.jpg
     */
    public static void storeImg(String strFile) throws Exception {
        int id = 0;
        File file = new File(strFile);
        FileInputStream fis = new FileInputStream(file);
        try {
            ps = conn.prepareStatement("insert "
                    + "into PIC values (?,?,?)");
            ps.setInt(1, id);
            ps.setString(2, file.getName());
            ps.setBinaryStream(3, fis, (int) file.length());
            ps.executeUpdate();
            System.out.println("file insert success ");
        } catch (SQLException e) {
            printLog(e);
            e.printStackTrace();
        } finally {
            ps.close();
            fis.close();
            conn.close();
        }
    }

    /**
     * 将指定路径的文件(比如：图片，word文档等)存储到数据库
     *
     * @param faceByte 要存放到数据库的文件路径，如D:\\a.jpg
     */
    public static void storeByteArray(byte[] faceByte) throws Exception {
        int id = 0;
        try {
            ps = conn.prepareStatement("update "
                    + "ug_face_data set face_data=? where id=1");
            ps.setBytes(1, faceByte);
            ps.executeUpdate();
            System.out.println("file insert success ");
        } catch (SQLException e) {
            printLog(e);
            e.printStackTrace();
        } finally {
            ps.close();
            conn.close();
        }
    }

    /**
     * 将指定路径的文件(比如：图片，word文档等)存储到数据库
     *
     * @param faceByte 要存放到数据库的文件路径，如D:\\a.jpg
     */
    public static void storeImageByteArray(byte[] faceByte) throws Exception {
        int id = 0;
        try {
            ps = conn.prepareStatement("update "
                    + "ug_face_data set img=? where id=1");
            ps.setBytes(1, faceByte);
            ps.executeUpdate();
            System.out.println("file insert success ");
        } catch (SQLException e) {
            printLog(e);
            e.printStackTrace();
        } finally {
            ps.close();
            conn.close();
        }
    }

    /**
     * 读取数据库文件（.sql），并执行sql语句
     */
    public static void executeAssetsSQL(Context mContext, String schemaName) {
        BufferedReader in = null;
        try {
            in = new BufferedReader(new InputStreamReader(mContext.getAssets()
                    .open(schemaName + ".sql")));

            System.out.println("路径:" + schemaName + ".sql");
            String line;
            String buffer = "";
            while ((line = in.readLine()) != null) {
                buffer += line;
                if (line.trim().endsWith(";")) {
                    execSQL(buffer.replace(";", ""));
                    buffer = "";
                }
            }
        } catch (IOException e) {
            Logger.e("db-error", e.toString());
        } finally {
            try {
                if (in != null)
                    in.close();
            } catch (IOException e) {
                Logger.e("db-error", e.toString());
            }
        }
    }

    /**
     * 打印 sql 异常
     *
     * @param e
     */
    private static void printLog(SQLException e) {
        Logger.e("SQLException: " + e.getMessage()
                + "\nSQLState: " + e.getSQLState()
                + "\nVendorError:" + e.getErrorCode());
    }

    /**
     * 获取用户信息
     *
     * @param groupId
     * @param userId
     * @return
     */
    public static User getUserInfo(String groupId, String userId) {
        if (TextUtils.isEmpty(groupId) || TextUtils.isEmpty(userId)) {
            return null;
        }
        User user = queryUser(groupId, userId);
        if (user != null) {
            List featureList = queryFeature(groupId, userId);
            user.setFeatureList(featureList);
        }
        return user;
    }

    /* *//**
     * 将存储在数据库中的文件(比如：图片，word文档等)读取到指定路径
     *
     * @param id 数据库里记录的id
     *//*
    public static void readImg(int id) throws Exception {
        byte[] buffer = new byte[4096];
        FileOutputStream outputImage = null;
        InputStream is = null;
        try {
            ps = conn.prepareStatement("select face_data from ug_face_data where id =?");
            ps.setInt(1, id);
            ResultSet rs = ps.executeQuery();
            rs.next();
            File file = new File(FileUtils.getFilePath() + "/image/", "a.data");
            if (!file.exists()) {
                file.createNewFile();
            }
            outputImage = new FileOutputStream(file);
            Blob blob = rs.getBlob("face_data");   //img为数据库存放图片字段名称
            is = blob.getBinaryStream();
            int size = 0;
            while ((size = is.read(buffer)) != -1) {
                outputImage.write(buffer, 0, size);
            }
            System.out.println("file read success ");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            is.close();
            outputImage.close();
            ps.close();
            conn.close();
        }
    }*/

    /**
     * 更新用户
     *
     * @param user
     * @return
     */
    public static boolean updateUser(User user) {
        boolean execResult = false;
        if (conn == null) {
            return execResult;
        }
        PreparedStatement ps = null;
        try {
            ps = conn.prepareStatement("update ug_feature_user set face_user_no='" + user.getFace_user_no() + "', door_id=" + user.getDoorId() + ", update_time='" + user.getUpdateTime() + "' where user_id='" + user.getUserId() + "';");
            ps.executeUpdate();

            for (Feature feature : user.getFeatureList()) {
                updateFeature(feature);
            }
            execResult = true;
            EventBus.getDefault().post("In:更新用户-" + user.getDoorId());
        } catch (SQLException e) {
            execResult = false;
            e.printStackTrace();
            printLog(e);
            EventBus.getDefault().post("In:更新用户失败-" + user.getUserId());
        } finally {
            try {
                if (ps != null) {
                    ps.close();
                    ps = null;
                }
            } catch (SQLException e) {
                e.printStackTrace();
                printLog(e);
                EventBus.getDefault().post("In:更新用户失败-" + user.getUserId());
            }
        }
        return execResult;
    }

    /**
     * 更新指定用户的人脸特征
     *
     * @return
     */
    public static boolean updateFeature(Feature feature) {
        boolean execResult = false;
        if (conn == null) {
            return execResult;
        }
        PreparedStatement ps = null;
        try {
            ps = conn.prepareStatement("update ug_feature set face_token=?,group_id=?,feature=?,image_name=?,update_time=?  where user_id=?");
            if (ps != null) {
                ps.setString(1, feature.getFaceToken());
                ps.setString(2, feature.getGroupId());
                ps.setBytes(3, feature.getFeature());
                ps.setString(4, feature.getImageName());
                ps.setLong(5, System.currentTimeMillis());
                ps.setString(6, feature.getUserId());
                ps.executeUpdate();
                execResult = true;
            } else {
                execResult = false;
            }
        } catch (SQLException e) {
            execResult = false;
            e.printStackTrace();
            printLog(e);
        } finally {
            try {
                if (ps != null) {
                    ps.close();
                    ps = null;
                }
            } catch (SQLException e) {
                e.printStackTrace();
                printLog(e);
            }
        }
        return execResult;
    }

    public void onInsert() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                String sql = "insert into users values(15, 'xiaoming')";
                MySqlUtil.execSQL(sql);
                Logger.i("onInsert", "onInsert");
            }
        }).start();
    }

    public void onDelete() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                String sql = "delete from users where name='hanmeimei'";
                MySqlUtil.execSQL(sql);
                Logger.i("onDelete", "onDelete");
            }
        }).start();
    }

    public void onUpdate() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                String sql = "update users set name='lilei' where name='liyanzhen'";
                MySqlUtil.execSQL(sql);
                Logger.i("onUpdate", "onUpdate");
            }
        }).start();
    }

    public void onQuery() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                MySqlUtil.execSQL("select * from users");
                Logger.i("onQuery", "onQuery");
            }
        }).start();
    }
}