时间：2021-07-01 10:21:17 帮助过：17人阅读
当需要向数据库发送一批SQL语句执行时，应避免向数据库一条条发送执行，采用批处理以提升执行效率
批处理有两种方式：
通过executeBath()方法批量处理执行SQL语句，返回一个int[]数组，该数组代表各句SQL的返回值
以下代码是以Statement方式实现批处理
/*
* Statement执行批处理
*
* 优点：
* 可以向数据库发送不同的SQL语句
* 缺点：
* SQL没有预编译
* 仅参数不同的SQL，需要重复写多条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‘)";
//将sql添加到批处理
statement.addBatch(sql1);
statement.addBatch(sql2);
//执行批处理
statement.executeBatch();
//清空批处理的sql
statement.clearBatch();
UtilsDemo.release(connection, statement, null);
以下方式以PreparedStatement方式实现批处理
/*
* PreparedStatement批处理
* 优点：
* SQL语句预编译了
* 对于同一种类型的SQL语句，不用编写很多条
* 缺点：
* 不能发送不同类型的SQL语句
*
* */
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"));
//添加到批处理中
preparedStatement.addBatch();
if (i %2 ==100) {
//执行批处理
preparedStatement.executeBatch();
//清空批处理【如果数据量太大，所有数据存入批处理，内存肯定溢出】
preparedStatement.clearBatch();
}
}
//不是所有的%2==100，剩下的再执行一次批处理
preparedStatement.executeBatch();
//再清空
preparedStatement.clearBatch();
UtilsDemo.release(connection, preparedStatement, null);
clob和blob
MySQL存储大文本是用Test【代替clob】，Test又分为4类
同理blob也有这4类
下面用JDBC连接MySQL数据库去操作大文本数据和二进制数据
/*
*用JDBC操作MySQL数据库去操作大文本数据
*
*setCharacterStream(int parameterIndex,java.io.Reader reader,long length)
*第二个参数接收的是一个流对象，因为大文本不应该用String来接收，String太大会导致内存溢出
*第三个参数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);
//获取到文件的路径
String path = Demo5.class.getClassLoader().getResource("BigTest").getPath();
File file = new File(path);
FileReader fileReader = new FileReader(file);
//第三个参数，由于测试的Mysql版本过低，所以只能用int类型的。高版本的不需要进行强转
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);
}
}
/*
* 读取大文本数据，通过ResultSet中的getCharacterStream()获取流对象数据
*
* */
@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);
}
}
/*
* 使用JDBC连接MYsql数据库操作二进制数据
* 如果我们要用数据库存储一个大视频的时候，数据库是存储不到的。
* 需要设置max_allowed_packet，一般我们不使用数据库去存储一个视频
* */
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);
//获取文件的路径和文件对象
String path = Demo6.class.getClassLoader().getResource("1.wmv").getPath();
File file = new File(path);
//调用方法
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();
//如果读取到数据，就把数据写到磁盘下
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);
}
}
下面用JDBC连接Oracle数据库去操作大文本数据和二进制数据
//使用JDBC连接Oracle数据库操作二进制数据
/*
* 对于Oracle数据库和Mysql数据库是有所不同的。
* 1.Oracle定义了BLOB字段，但是这个字段不是真正地存储二进制数据
* 2.向这个字段存一个BLOB指针，获取到Oracle的BLOB对象,把二进制数据放到这个指针里面,指针指向BLOB字段
* 3.需要事务支持
*
* */
public class Demo7 {
@Test
public void add() {
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
connection = UtilsDemo.getConnection();
//开启事务
connection.setAutoCommit(false);
//插入一个BLOB指针
String sql = "insert into test4(id,image) values(?,empty_blob())";
preparedStatement = connection.prepareStatement(sql);
preparedStatement.setInt(1, 1);
preparedStatement.executeUpdate();
//把BLOB指针查询出来,得到BLOB对象
String sql2 = "select image from test4 where id= ? for update";
preparedStatement = connection.prepareStatement(sql2);
preparedStatement.setInt(1, 1);
resultSet = preparedStatement.executeQuery();
if (resultSet.next()) {
//得到Blob对象--当成是Oracle的Blob,不是JDBC的,所以要强转[导的是oracle.sql.BLOB包]
BLOB blob = (BLOB) resultSet.getBlob("image");
//写入二进制数据
OutputStream outputStream = blob.getBinaryOutputStream();
//获取到读取文件读入流
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()) {
//获取到BLOB对象
BLOB blob = (BLOB) resultSet.getBlob("image");
//将数据读取到磁盘上
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);
}
}
}
对于JDBC连接Oracle数据库操作CLOB数据,我就不再重复了,操作跟BLOB几乎相同
应用场景:
有一张老师表，一张学生表。现在来了一个新的老师，学生要跟着新老师上课。
我首先要知道老师的id编号是多少，学生才能知道跟着哪个老师学习【学生外键参照老师主键】。
@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) {
//获取到自动主键列的值
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);
}
调用存储过程的语法：
{call <procedure-name>[(<arg1>,<arg2>, ...)]}调用函数的语法：
{?= call <procedure-name>[(<arg1>,<arg2>, ...)]}如果是Output类型的，那么在JDBC调用的时候是要注册的。如下代码所示：
/*
jdbc调用存储过程
delimiter $$
CREATE PROCEDURE demoSp(IN inputParam VARCHAR(255), INOUT inOutParam varchar(255))
BEGIN
SELECT CONCAT(‘zyxw---‘, inputParam) into inOutParam;
END $$
delimiter ;
*/
//我们在JDBC调用存储过程,就像在调用方法一样
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");
//注册第2个参数,类型是VARCHAR
callableStatement.registerOutParameter(2, Types.VARCHAR);
callableStatement.execute();
//获取传出参数[获取存储过程里的值]
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();
}
}
}
参考资料：
----------------------------------------------------------------------------------过程
#修改mysql语句的结果符为//
mysql > delimiter //
#定义一个过程，获取users表总记录数，将10设置到变量count中
create procedure simpleproc(out count int)
begin
select count(id) into count from users;
end
//
#修改mysql语句的结果符为;
mysql > delimiter ;
#调用过程，将结果覆给变量a，@是定义变量的符号
call simpleproc(@a);
#显示变量a的值
select @a;
//以下是Java调用Mysql的过程
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");
----------------------------------------------------------------------------------函数
#修改mysql语句的结果符为//
mysql > delimiter //
#定义一个函数，完成字符串拼接
create function hello( s char(20) ) returns char(50)
return concat(‘hello，‘,s,‘!‘);
//
#修改mysql语句的结果符为;
mysql > delimiter ;
#调用函数
select hello(‘world‘);
//以下是Java调用Mysql的函数
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);如果文章有错的地方欢迎指正，大家互相交流。习惯在微信看技术文章的同学，可以关注微信公众号:Java3y
JDBC【PreparedStatment、批处理、处理二进制、自动主键、调用存储过程、函数】
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