笔记：JDBC 数据库

• 数据库 URL

  在连接数据库时，我们必须使用各种与数据库类型相关的参数，例如主机名、端口号和数据库名称等，JDBC使用了一种与普通URL相类似的语法来描述数据库，JDBC URL 一般语法为：

  jdbc:subprotocol:other stuff

  其中 subprotocol 用于选择连接到数据库的具体驱动程序

  other stuff 参数的格式随所使用的 subprotocol 不同而不同

  示例：

  MySQL 数据库：jdbc:mysql://localhost:port/dbname

• 注册驱动器类

  某些JDBC 的JAR文件将自动注册驱动器类，在这种情况下可以跳过手动注册步骤，在驱动程序JAR文件中的 META-INF/services/java.sql.Driver 存在这个文件就表示自动注册。

  如果驱动程序JAR文件不支持自动注册，那就需要找出数据库提供商使用的JDBC驱动器类名字，通过使用 DriverManager 可以在Java程序中加载驱动器类，例如：

  Class.forName("驱动器类");

  这条语句将使驱动器类被加载，由此执行可以注册驱动器的静态初始化器。

• 连接到数据库

  使用 java.sql 包下的 DriverManager 驱动管理器类的 getConnection 方法获取数据库连接对象，在获取数据库连接对象需要传入数据库URL和用户名等验证信息，MySQL示例代码：

  package org.drsoft;

  import java.sql.Connection;

  import java.sql.DriverManager;

  import java.sql.SQLException;

  public class JDBCManager {

      public static
  void
  main(String[] args) throws SQLException {

          String jdbcUrl="jdbc:mysql://192.168.94.128:3306/hibernatedb";

          String userName="dev";

          String password="liyong";

          
   

          Connection conn = DriverManager.getConnection(jdbcUrl, userName,password);

   
   

  conn.close();

      }

  }

• 执行SQL语句

  在执行SQL 语句之前，首先需要创建一个Statement 对象，要创建 Statement 对象，需要使用调用 DriverManager.getConnection 方法获取获取的 Connection 对象，使用 Connection 对象调用 createStatement 方法来创建，代码示例如下：

  • 执行插入/更新/删除SQL语句

    package org.drsoft;

    import java.sql.*;

    public class JDBCManager {

        public static
    void
    main(String[] args) throws SQLException {

            String jdbcUrl="jdbc:mysql://192.168.94.128:3306/hibernatedb";

            String userName="dev";

            String password="liyong";

            
     

            Connection conn = DriverManager.getConnection(jdbcUrl, userName,password);

            Statement statement= conn.createStatement();

            String sql="Insert Into Transit_Record(Total_Count,Total_Trade_Amt) Values(101,1023)";

            
     

            int updateRowCount = statement.executeUpdate(sql);

            System.out.println("executeUpdate row "+updateRowCount);

     
     

    conn.close();

        }

    }

  • 执行插入并获取自增长主键值

    package org.drsoft;

    import java.sql.*;

    import java.text.SimpleDateFormat;

    public class JDBCManager {

        public static
    void
    main(String[] args) throws SQLException {

            String jdbcUrl = "jdbc:mysql://192.168.94.128:3306/hibernatedb";

            String userName = "dev";

            String password = "liyong";

     
     

            Connection conn = DriverManager.getConnection(jdbcUrl, userName, password);

            String insertDataTimeSql =

    "Insert Into Transit_Record(Total_Count,Total_Trade_Amt,Create_Time) Values(101,1023,?)";

            PreparedStatement ps = conn.prepareStatement(insertDataTimeSql, Statement.RETURN_GENERATED_KEYS);

            ps.setString(1, "2016-01-01 23:44:33");

     
     

            int rowCount = ps.executeUpdate();

            ResultSet keyResultSet = ps.getGeneratedKeys();

            if (keyResultSet.next()) {

                System.out.println("insertDateTime rowCount=" + rowCount + "\tKey=" + keyResultSet.getInt(1));

            }

     
     

            conn.close();

        }

    }

  • 执行查询SQL语句

    package org.drsoft;

    import java.sql.*;

    public class JDBCManager {

        public static
    void
    main(String[] args) throws SQLException {

            String jdbcUrl = "jdbc:mysql://192.168.94.128:3306/hibernatedb";

            String userName = "dev";

            String password = "liyong";

     
     

            Connection conn = DriverManager.getConnection(jdbcUrl, userName, password);

            Statement statement = conn.createStatement();

            String querySql = "Select * from Transit_Record Order by Record_ID DESC Limit 0,10";

            ResultSet resultSet = statement.executeQuery(querySql);

            while (resultSet.next()) {

                System.out.println(

                        "RecordID=" + resultSet.getInt("Record_ID") + "\tTotalCount=" +

    resultSet.getInt("Total_Count"));

            }

     
     

    conn.close();

        }

    }

  • 执行参数SQL语句

    package org.drsoft;

    import java.sql.*;

    public class JDBCManager {

        public static
    void
    main(String[] args) throws SQLException {

            String jdbcUrl = "jdbc:mysql://192.168.94.128:3306/hibernatedb";

            String userName = "dev";

            String password = "liyong";

     
     

            Connection conn = DriverManager.getConnection(jdbcUrl, userName, password);

            String querySingleSql = "Select * from Transit_Record Where Record_ID = ?";

            
     

            PreparedStatement preparedStatement = conn.prepareStatement(querySingleSql);

            preparedStatement.setInt(1, 6624);

            ResultSet resultSet = preparedStatement.executeQuery();

            while (resultSet.next()) {

                System.out.println(

                        "RecordID=" + resultSet.getInt("Record_ID") + "\tTotalCount=" +

    resultSet.getInt("Total_Count"));

            }

            
     

            conn.close();

        }

    }

  • 读取 LOB

    在SQL中，二进制大对象称为 BLOB，字符型大对象称为CLOB，要读取LOB，需要执行SELECT语句，然后在ResultSet 对象上调用 getBlob 或 getClob方法，这样就可以获取Blob或Clob类型对象，然后分别通过调用 getBytes 或 getBinaryStream 获取二进制数据；通过调用 getSubString 或 getCharacterStream 获取字符串数据，代码示例：

    package org.drsoft;

    import java.sql.*;

    public class JDBCManager {

        public static
    void
    main(String[] args) throws SQLException {

            String jdbcUrl = "jdbc:mysql://192.168.94.128:3306/hibernatedb";

            String userName = "dev";

            String password = "liyong";

     
     

            Connection conn = DriverManager.getConnection(jdbcUrl, userName, password);

            String querySingleSql = "Select Cover from Transit_Record Where Record_ID = ?";

            
     

            PreparedStatement preparedStatement = conn.prepareStatement(querySingleSql);

            preparedStatement.setInt(1, 6624);

            ResultSet resultSet = preparedStatement.executeQuery();

            if(resultSet.next()) {

                Blob blob = resultSet.getBlob(1);

                Image coverImage ImageIo.read(blob.getBinaryStream();

            }

            
     

            conn.close();

        }

    }

  • 写入LOB

    要将LOB保存到数据库，需要在
    Connection
    对象上调用
    createBlob
    或
    createClob，然后获取一个用于该LOB的输出流，写入数据，并将该对象存储到数据库中，示例代码：

    package org.drsoft;

     import java.sql.*;

    public class JDBCManager {

         public static
    void
    main(String[] args) throws SQLException {

              String jdbcUrl = "jdbc:mysql://192.168.94.128:3306/hibernatedb";

              String userName = "dev";

             
    String password = "liyong";

                
     

              Connection conn = DriverManager.getConnection(jdbcUrl, userName, password);

              String querySingleSql = "Insert Into Transit_Record(Cover) Values(?)";

                        
     

              byte[] buff = new
    byte[1024];

              Blob newBlob = conn.createBlob();

              newBlob.setBytes(0,newBlob);

              PreparedStatement preparedStatement = conn.prepareStatement(querySingleSql);

              preparedStatement.setInt(1, newBlob);

              int updateRowCount = preparedStatement.executeUpdate();

                        
     

             conn.close();

      }

• 调用存储过程
  • 查询存储过程

    package org.drsoft;

    import java.sql.*;

    import java.text.SimpleDateFormat;

    public class JDBCManager {

        public static
    void
    main(String[] args) throws SQLException {

            String jdbcUrl = "jdbc:mysql://192.168.94.128:3306/hibernatedb";

            String userName = "dev";

            String password = "liyong";

     
     

            Connection conn = DriverManager.getConnection(jdbcUrl, userName, password);

            String procCallSql = "call procGet_Trade_Report(?,?)";

            PreparedStatement procPreparedtatement = conn.prepareStatement(procCallSql);

            procPreparedtatement.setInt(1, 1000);

            procPreparedtatement.setInt(2, 4000);

     
     

            ResultSet procResultSet = procPreparedtatement.executeQuery();

            if (procResultSet.next()) {

                System.out.println("procGet_Trade_Report SumTotalAmt=" + procResultSet.getLong(1)

                        + "\tSumTotalCount=" + procResultSet.getLong(2));

            }

     
     

            conn.close();

        }

    }

  • 输入和输出参数储存过程

    package org.drsoft;

    import java.sql.*;

    import java.text.SimpleDateFormat;

    public class JDBCManager {

        public static
    void
    main(String[] args) throws SQLException {

            String jdbcUrl = "jdbc:mysql://192.168.94.128:3306/hibernatedb";

            String userName = "dev";

            String password = "liyong";

     
     

            Connection conn = DriverManager.getConnection(jdbcUrl, userName, password);

            String procReturnCallSql = "{call procTransit_Record_Create(?,?,?)}";

            CallableStatement callPreParedStatement = conn.prepareCall(procReturnCallSql);

            // 第一个参数是输出参数

            callPreParedStatement.registerOutParameter(1, Types.INTEGER);

            callPreParedStatement.setInt(2, 1000);

            callPreParedStatement.setLong(3, new
    Long(4000));

            // 调用结果返回 true 则表示返回的是结果集，返回 false 表示结果是更新计数或没有结果

            callPreParedStatement.execute();

            // 获取输出参数值

            System.out.println("procTransit_Record_Create Record_ID=" + callPreParedStatement.getInt(1));

     
     

            conn.close();

    }

    }

• SQL转义

  "转义"语法支持各种数据库普遍支持的特性，当是数据库使用的是与数据库相关的语法变体，因此，将转义语法转译为特定的数据库语法是JDBC驱动程序的任务之一，在LIKE子句中的转义字符，"_"和"%"字符在LIKE子句中有特殊含义，用来匹配一个字符或一个字符序列，如果需要匹配所有包含"_"的字符串，就必须使用"!"转义符

• 数据库事务

  默认情况下，数据库连接处于自动提交模式，每个SQL语句一旦被提交给数据库，一旦命名被提交，就无法对他进行回滚操作，在使用事务时，需要关闭这个默认值。

  package org.drsoft;

  import java.sql.*;

  import java.text.SimpleDateFormat;

  public class JDBCManager {

      public static
  void
  main(String[] args) throws SQLException {

          String jdbcUrl = "jdbc:mysql://192.168.94.128:3306/hibernatedb";

          String userName = "dev";

          String password = "liyong";

   
   

          Connection conn = DriverManager.getConnection(jdbcUrl, userName, password);

          // 设置自动提交为 false

          conn.setAutoCommit(false);

          String procReturnCallSql = "{call procTransit_Record_Create(?,?,?)}";

          CallableStatement callPreParedStatement = conn.prepareCall(procReturnCallSql);

          callPreParedStatement.registerOutParameter(1, Types.INTEGER);

          callPreParedStatement.setInt(2, 1000);

          callPreParedStatement.setLong(3, new
  Long(4000));

          // 调用结果返回 true 则表示返回的是结果集，返回 false 表示结果是更新计数或没有结果

          callPreParedStatement.execute();

          System.out.println("Record_ID=" + callPreParedStatement.getInt(1)+"\tCommit");

          // 提交事务

          conn.commit();

          
   

          callPreParedStatement.execute();

          System.out.println("Record_ID=" + callPreParedStatement.getInt(1)+"\tRollback");

          callPreParedStatement.execute();

          System.out.println("Record_ID=" + callPreParedStatement.getInt(1)+"\tRollback");

          
   

          // 回滚事务

          conn.rollback();

          conn.close();

      }

  }

• 批量更新

  如果有一个程序需要执行许多INSERT语句，以便将数据填入数据库表中，此时可以使用批量更新的方法来提高程序性能，在使用批量更新时，可以支持INSERT、UPDATE、DELETE和数据库定义语句相关。

  package org.drsoft;

  import java.sql.*;

  import java.text.SimpleDateFormat;

  import java.util.Calendar;

  import java.util.Locale;

  public class JDBCManager {

      public static
  void
  main(String[] args) throws SQLException {

          String jdbcUrl = "jdbc:mysql://192.168.94.128:3306/hibernatedb";

          String userName = "dev";

          String password = "liyong";

   
   

          Connection conn = DriverManager.getConnection(jdbcUrl, userName, password);

          String sql = "Insert Into Transit_Record(Total_Count,Total_Trade_Amt,Create_Time) Values(101,1023,?)";

          PreparedStatement batchStatement = conn.prepareStatement(sql);

          SimpleDateFormat df = new
  SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

          Calendar calendar = Calendar.getInstance(Locale.CHINA);

          for (int i = 0; i < 10; i++) {

   
   

              calendar.set(Calendar.SECOND, calendar.get(Calendar.SECOND) + 1);

              batchStatement.setString(1, df.format(calendar.getTime()));

              // 增加一条语句和相关参数

              batchStatement.addBatch();

          }

          // 批量执行

          int[] executeResult = batchStatement.executeBatch();

          for (int i = 0; i < executeResult.length; i++) {

              System.out.println("Execute Result " + executeResult[i]);

          }

          conn.close();

      }

  }