A comprehensive explanation of JDBC’s PreparedStatement

1 year ago
Sophia Anderson
2 minutes

The PreparedStatement interface in JDBC, which extends the Statement interface, is used to precompile SQL statements to improve query efficiency and prevent SQL injection.

In contrast to a Statement, a PreparedStatement is pre-compiled before execution. This means that the parameters in the SQL statement are replaced with placeholders (?) and then sent to the database for compilation. When the statement needs to be executed, the placeholders can be set with specific values using the setXXX() method, and then the execute() or executeUpdate() method can be called to perform the query or update operation.

There are several benefits of using PreparedStatement:

  1. Improving performance: PreparedStatement precompiles the SQL statement and stores it in cache. When executing the same SQL statement again, only passing parameter values to it is needed, avoiding recompiling and enhancing query efficiency.
  2. Prevent SQL injection: PreparedStatement effectively prevents SQL injection attacks by performing strict type checking and escaping of parameters.

The sample code is shown below:

// 创建PreparedStatement对象
PreparedStatement preparedStatement = connection.prepareStatement("SELECT * FROM user WHERE name = ?");

// 设置参数值
preparedStatement.setString(1, "John");

// 执行查询操作
ResultSet resultSet = preparedStatement.executeQuery();

// 处理查询结果
while(resultSet.next()) {
    // 处理每一行数据
}

// 关闭资源
resultSet.close();
preparedStatement.close();

In the above example, first a PreparedStatement object is created using connection.prepareStatement() method, then placeholders are set using setXXX() method, next executeQuery() method is called to perform the query operation, and finally the query results are processed.

It is important to note that the index of placeholders starts at 1, not 0. Additionally, when setting parameter values, it is necessary to choose the appropriate setXXX() method based on the actual situation to ensure the correct parameter type.

In summary, PreparedStatement is an interface in JDBC used for precompiling SQL statements, which helps improve query efficiency and prevent SQL injection attacks by precompiling and binding parameters. It is recommended to use PreparedStatement for executing SQL statements in actual development.

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