数据库中使用Blob处理二进制数据

长文本（Clob）和二进制文件（Blob）的处理难点其实不再JDBC上，而是在输入输出上。

package cn.itcast.jdbc;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

//blob最大64K
public class BlobTest {

    public static void main(String[] args) throws SQLException, IOException {
// create();
        read();
    }

    // 跟clob差不多，只是修改了Reader为InputStream，并setBinaryStream()设置二进制流
    static void create() throws SQLException, IOException {
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;

        try {
            conn = JdbcUtils.getConnection();
            String sql = "insert into blob_test(big_bit)values(?)";
            ps = conn.prepareStatement(sql);

            File file = new File("mudan.jpg");
            InputStream in = new BufferedInputStream(new FileInputStream(file));

            ps.setBinaryStream(1, in, (int) file.length()); // 字节流

            int i = ps.executeUpdate();

            in.close();
            System.out.println("i=" + i);

        } finally {
            JdbcUtils.free(rs, ps, conn);
        }
    }

    static void read() throws SQLException, IOException {
        Connection conn = null;
        Statement st = null;
        ResultSet rs = null;

        try {
            conn = JdbcUtils.getConnection(); 
            st = conn.createStatement();

            rs = st.executeQuery("select big_bit from blob_test");

            while (rs.next()) {
// 方法1 
// Blob blob = rs.getBlob("1"); 
// InputStream in = blob.getBinaryStream();

// 方法2，这个方法更好
                InputStream in=rs.getBinaryStream(1);   
                File file = new File("COPY.jpg");
                OutputStream out = new BufferedOutputStream(new FileOutputStream(file)) ;
                byte[] buff = new byte[1024]; // 缓冲区
                for (int i = 0; (i = in.read(buff)) > 0;)
                    out.write(buff, 0, i);

                out.close();
                in.close();
            }

        } finally {
            JdbcUtils.free(rs, st, conn);
        }
    }
}