JDBC【PreparedStatment、批處理、處理二進制、自動主鍵、調用存儲過程、函數】

1.PreparedStatement對象

PreparedStatement對象繼承Statement對象，它比Statement對象更強大，使用起來更簡單

1. Statement對象編譯SQL語句時，若是SQL語句有變量，就須要使用分隔符來隔開，若是變量很是多，就會使SQL變得很是複雜。PreparedStatement可使用佔位符，簡化sql的編寫
2. Statement會頻繁編譯SQL。PreparedStatement可對SQL進行預編譯，提升效率，預編譯的SQL存儲在PreparedStatement對象中
3. PreparedStatement防止SQL注入。【Statement經過分隔符'++',編寫永等式，能夠不須要密碼就進入數據庫】

//模擬查詢id爲2的信息
        String id = "2";

        Connection connection = UtilsDemo.getConnection();

        String sql = "SELECT * FROM users WHERE id = ?";
        PreparedStatement preparedStatement = connection.preparedStatement(sql);

        //第一個參數表示第幾個佔位符【也就是?號】，第二個參數表示值是多少
        preparedStatement.setString(1,id);

        ResultSet resultSet = preparedStatement.executeQuery();

        if (resultSet.next()) {
            System.out.println(resultSet.getString("name"));
        }

        //釋放資源
        UtilsDemo.release(connection, preparedStatement, resultSet);

複製代碼

---

2.批處理

當須要向數據庫發送一批SQL語句執行時，應避免向數據庫一條條發送執行，採用批處理以提高執行效率

批處理有兩種方式：

1. Statement
2. PreparedStatement

經過executeBath()方法批量處理執行SQL語句，返回一個int[]數組，該數組表明各句SQL的返回值

如下代碼是以Statement方式實現批處理

/* * Statement執行批處理 * * 優勢： * 能夠向數據庫發送不一樣的SQL語句 * 缺點： * SQL沒有預編譯 * 僅參數不一樣的SQL，須要重複寫多條SQL * */
        Connection connection = UtilsDemo.getConnection();

        Statement statement = connection.createStatement();
        String sql1 = "UPDATE users SET name='zhongfucheng' WHERE id='3'";
        String sql2 = "INSERT INTO users (id, name, password, email, birthday)" +
                " VALUES('5','nihao','123','ss@qq.com','1995-12-1')";

        //將sql添加到批處理
        statement.addBatch(sql1);
        statement.addBatch(sql2);

        //執行批處理
        statement.executeBatch();

        //清空批處理的sql
        statement.clearBatch();

        UtilsDemo.release(connection, statement, null);


複製代碼

如下方式以PreparedStatement方式實現批處理

/* * PreparedStatement批處理 * 優勢： * SQL語句預編譯了 * 對於同一種類型的SQL語句，不用編寫不少條 * 缺點： * 不能發送不一樣類型的SQL語句 * * */
        Connection connection = UtilsDemo.getConnection();

        String sql = "INSERT INTO test(id,name) VALUES (?,?)";
        PreparedStatement preparedStatement = connection.prepareStatement(sql);

        for (int i = 1; i <= 205; i++) {
            preparedStatement.setInt(1, i);
            preparedStatement.setString(2, (i + "zhongfucheng"));

            //添加到批處理中
            preparedStatement.addBatch();

            if (i %2 ==100) {

                //執行批處理
                preparedStatement.executeBatch();

                //清空批處理【若是數據量太大，全部數據存入批處理，內存確定溢出】
                preparedStatement.clearBatch();
            }

        }
        //不是全部的%2==100，剩下的再執行一次批處理
        preparedStatement.executeBatch();

        //再清空
        preparedStatement.clearBatch();

        UtilsDemo.release(connection, preparedStatement, null);




複製代碼

---

3.處理大文本和二進制數據

clob和blob

• clob用於存儲大文本
• blob用於存儲二進制數據

---

MYSQL

MySQL存儲大文本是用Test【代替clob】，Test又分爲4類

• TINYTEXT
• TEXT
• MEDIUMTEXT
• LONGTEXT

同理blob也有這4類

---

下面用JDBC鏈接MySQL數據庫去操做大文本數據和二進制數據

/* *用JDBC操做MySQL數據庫去操做大文本數據 * *setCharacterStream(int parameterIndex,java.io.Reader reader,long length) *第二個參數接收的是一個流對象，由於大文本不該該用String來接收，String太大會致使內存溢出 *第三個參數接收的是文件的大小 * * */
public class Demo5 {

    @Test
    public void add() {

        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        try {
            connection = JdbcUtils.getConnection();
            String sql = "INSERT INTO test2 (bigTest) VALUES(?) ";
            preparedStatement = connection.prepareStatement(sql);

            //獲取到文件的路徑
            String path = Demo5.class.getClassLoader().getResource("BigTest").getPath();
            File file = new File(path);
            FileReader fileReader = new FileReader(file);

            //第三個參數，因爲測試的Mysql版本太低，因此只能用int類型的。高版本的不須要進行強轉
            preparedStatement.setCharacterStream(1, fileReader, (int) file.length());

            if (preparedStatement.executeUpdate() > 0) {
                System.out.println("插入成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.release(connection, preparedStatement, null);
        }


    }

    /* * 讀取大文本數據，經過ResultSet中的getCharacterStream()獲取流對象數據 * * */
    @Test
    public void read() {

        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        try {
            connection = JdbcUtils.getConnection();
            String sql = "SELECT * FROM test2";
            preparedStatement = connection.prepareStatement(sql);
            resultSet = preparedStatement.executeQuery();

            if (resultSet.next()) {

                Reader reader = resultSet.getCharacterStream("bigTest");

                FileWriter fileWriter = new FileWriter("d:\\abc.txt");
                char[] chars = new char[1024];
                int len = 0;
                while ((len = reader.read(chars)) != -1) {
                    fileWriter.write(chars, 0, len);
                    fileWriter.flush();
                }
                fileWriter.close();
                reader.close();

            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.release(connection, preparedStatement, resultSet);
        }
        
    }




複製代碼

---

/* * 使用JDBC鏈接MYsql數據庫操做二進制數據 * 若是咱們要用數據庫存儲一個大視頻的時候，數據庫是存儲不到的。 * 須要設置max_allowed_packet，通常咱們不使用數據庫去存儲一個視頻 * */
public class Demo6 {

    @Test
    public void add() {


        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;


        try {
            connection = JdbcUtils.getConnection();
            String sql = "INSERT INTO test3 (blobtest) VALUES(?)";
            preparedStatement = connection.prepareStatement(sql);

            //獲取文件的路徑和文件對象
            String path = Demo6.class.getClassLoader().getResource("1.wmv").getPath();
            File file = new File(path);

            //調用方法
            preparedStatement.setBinaryStream(1, new FileInputStream(path), (int)file.length());

            if (preparedStatement.executeUpdate() > 0) {

                System.out.println("添加成功");
            }

        } catch (SQLException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.release(connection, preparedStatement, null);
        }

    }

    @Test
    public void read() {


        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;


        try {
            connection = JdbcUtils.getConnection();
            String sql = "SELECT * FROM test3";
            preparedStatement = connection.prepareStatement(sql);

            resultSet = preparedStatement.executeQuery();


            //若是讀取到數據，就把數據寫到磁盤下
            if (resultSet.next()) {
                InputStream inputStream = resultSet.getBinaryStream("blobtest");
                FileOutputStream fileOutputStream = new FileOutputStream("d:\\aa.jpg");

                int len = 0;
                byte[] bytes = new byte[1024];
                while ((len = inputStream.read(bytes)) > 0) {

                    fileOutputStream.write(bytes, 0, len);

                }
                fileOutputStream.close();
                inputStream.close();

            }

        } catch (SQLException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.release(connection, preparedStatement, null);
        }

    }



複製代碼

Oracle

下面用JDBC鏈接Oracle數據庫去操做大文本數據和二進制數據

//使用JDBC鏈接Oracle數據庫操做二進制數據
    
/* * 對於Oracle數據庫和Mysql數據庫是有所不一樣的。 * 1.Oracle定義了BLOB字段，可是這個字段不是真正地存儲二進制數據 * 2.向這個字段存一個BLOB指針，獲取到Oracle的BLOB對象,把二進制數據放到這個指針裏面,指針指向BLOB字段 * 3.須要事務支持 * * */
public class Demo7 {
    @Test
    public void add() {


        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        try {
            connection = UtilsDemo.getConnection();

            //開啓事務
            connection.setAutoCommit(false);

            //插入一個BLOB指針
            String sql = "insert into test4(id,image) values(?,empty_blob())";
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setInt(1, 1);
            preparedStatement.executeUpdate();

            //把BLOB指針查詢出來,獲得BLOB對象
            String sql2 = "select image from test4 where id= ? for update";
            preparedStatement = connection.prepareStatement(sql2);
            preparedStatement.setInt(1, 1);
            resultSet = preparedStatement.executeQuery();

            if (resultSet.next()) {
                //獲得Blob對象--當成是Oracle的Blob,不是JDBC的,因此要強轉[導的是oracle.sql.BLOB包]
                BLOB  blob = (BLOB) resultSet.getBlob("image");

                //寫入二進制數據
                OutputStream outputStream = blob.getBinaryOutputStream();

                //獲取到讀取文件讀入流
                InputStream inputStream = Demo7.class.getClassLoader().getResourceAsStream("01.jpg");

                int len=0;
                byte[] bytes = new byte[1024];
                while ((len = inputStream.read(bytes)) > 0) {

                    outputStream.write(bytes, 0, len);
                }
                outputStream.close();
                inputStream.close();
				connection.setAutoCommit(true);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            UtilsDemo.release(connection, preparedStatement, null);
        }

    }

    @Test
    public void find() {
        
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        try {
            connection = UtilsDemo.getConnection();
            String sql = "SELECT * FROM test4 WHERE id=1";

            preparedStatement = connection.prepareStatement(sql);
            resultSet = preparedStatement.executeQuery();

            if (resultSet.next()) {

                //獲取到BLOB對象
                BLOB blob = (BLOB) resultSet.getBlob("image");

                //將數據讀取到磁盤上
                InputStream inputStream = blob.getBinaryStream();
                FileOutputStream fileOutputStream = new FileOutputStream("d:\\zhongfucheng.jpg");
                int len=0;
                byte[] bytes = new byte[1024];

                while ((len = inputStream.read(bytes)) > 0) {

                    fileOutputStream.write(bytes, 0, len);
                }

                inputStream.close();
                fileOutputStream.close();

            }

        } catch (SQLException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            UtilsDemo.release(connection, preparedStatement, null);
        }
    }
}



複製代碼

對於JDBC鏈接Oracle數據庫操做CLOB數據,我就再也不重複了,操做跟BLOB幾乎相同

---

4.獲取數據庫的自動主鍵列

爲何要獲取數據庫的自動主鍵列數據?

應用場景:

有一張老師表，一張學生表。如今來了一個新的老師，學生要跟着新老師上課。

我首先要知道老師的id編號是多少，學生才能知道跟着哪一個老師學習【學生外鍵參照老師主鍵】。

---

@Test
    public void test() {

        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        try {
            connection = JdbcUtils.getConnection();

            String sql = "INSERT INTO test(name) VALUES(?)";
            preparedStatement = connection.prepareStatement(sql);

            preparedStatement.setString(1, "ouzicheng");

            if (preparedStatement.executeUpdate() > 0) {

                //獲取到自動主鍵列的值
                resultSet = preparedStatement.getGeneratedKeys();

                if (resultSet.next()) {
                    int id = resultSet.getInt(1);
                    System.out.println(id);
                }
            }
            
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.release(connection, preparedStatement, null);
        }




複製代碼

---

5.調用數據庫的存儲過程

調用存儲過程的語法：

{call <procedure-name>[(<arg1>,<arg2>, ...)]}
複製代碼

調用函數的語法：

{?= call <procedure-name>[(<arg1>,<arg2>, ...)]}
複製代碼

若是是Output類型的，那麼在JDBC調用的時候是要註冊的。以下代碼所示：

/* jdbc調用存儲過程 delimiter $$ CREATE PROCEDURE demoSp(IN inputParam VARCHAR(255), INOUT inOutParam varchar(255)) BEGIN SELECT CONCAT('zyxw---', inputParam) into inOutParam; END $$ delimiter ; */
//咱們在JDBC調用存儲過程,就像在調用方法同樣
public class Demo9 {

    public static void main(String[] args) {
        Connection connection = null;
        CallableStatement callableStatement = null;

        try {
            connection = JdbcUtils.getConnection();
            
            callableStatement = connection.prepareCall("{call demoSp(?,?)}");

            callableStatement.setString(1, "nihaoa");
            
            //註冊第2個參數,類型是VARCHAR
            callableStatement.registerOutParameter(2, Types.VARCHAR);
            callableStatement.execute();
            
			//獲取傳出參數[獲取存儲過程裏的值]
            String result = callableStatement.getString(2);
            System.out.println(result);

        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            try {
                connection.close();
                callableStatement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

    }


複製代碼

參考資料：

----------------------------------------------------------------------------------過程

#修改mysql語句的結果符爲//
mysql > delimiter //

#定義一個過程，獲取users表總記錄數，將10設置到變量count中
create procedure simpleproc(out count int)
begin
    select count(id) into count from users;
end
//

#修改mysql語句的結果符爲;
mysql > delimiter ;

#調用過程，將結果覆給變量a，@是定義變量的符號
call simpleproc(@a);

#顯示變量a的值
select @a;

//如下是Java調用Mysql的過程
	String sql = "{call simpleproc(?)}";
	Connection conn = JdbcUtil.getConnection();
	CallableStatement cstmt = conn.prepareCall(sql);
	cstmt.registerOutParameter(1,Types.INTEGER);
	cstmt.execute();
	Integer count = cstmt.getInt(1);
	System.out.println("共有" + count + "人");

----------------------------------------------------------------------------------函數

#修改mysql語句的結果符爲//
mysql > delimiter //

#定義一個函數，完成字符串拼接
create function hello( s char(20) ) returns char(50) 
return concat('hello，',s,'!');
//

#修改mysql語句的結果符爲;
mysql > delimiter ;

#調用函數
select hello('world');

//如下是Java調用Mysql的函數
	String sql = "{? = call hello(?)}";
	Connection conn = JdbcUtil.getConnection();
	CallableStatement cstmt = conn.prepareCall(sql);
	cstmt.registerOutParameter(1,Types.VARCHAR);
	cstmt.setString(2,"zhaojun");
	cstmt.execute();
	String value = cstmt.getString(1);
	System.out.println(value);
	JdbcUtil.close(cstmt);
	JdbcUtil.close(conn);

複製代碼

---

若是文章有錯的地方歡迎指正，你們互相交流。習慣在微信看技術文章的同窗，能夠關注微信公衆號:Java3y