数据库中使用Blob处理二进制数据

Myth丶恋晨 2022-08-09 00:48 273阅读 0赞

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);
            }
        }
    }