准备语句忽略SQL注入，提高了准备语句的安全性

PreparedStatement的优点:

Precompilation and DB-side caching of the SQL statement leads to overall faster execution and the ability to reuse the same SQL statement in batches. Automatic prevention of SQL injection attacks by builtin escaping of quotes and other special characters. Note that this requires that you use any of the PreparedStatement setXxx() methods to set the values preparedStatement = connection.prepareStatement("INSERT INTO Person (name, email, birthdate, photo) VALUES (?, ?, ?, ?)"); preparedStatement.setString(1, person.getName()); preparedStatement.setString(2, person.getEmail()); preparedStatement.setTimestamp(3, new Timestamp(person.getBirthdate().getTime())); preparedStatement.setBinaryStream(4, person.getPhoto()); preparedStatement.executeUpdate(); and thus don't inline the values in the SQL string by string-concatenating. preparedStatement = connection.prepareStatement("INSERT INTO Person (name, email) VALUES ('" + person.getName() + "', '" + person.getEmail() + "'"); preparedStatement.executeUpdate(); Eases setting of non-standard Java objects in a SQL string, e.g. Date, Time, Timestamp, BigDecimal, InputStream (Blob) and Reader (Clob). On most of those types you can't "just" do a toString() as you would do in a simple Statement. You could even refactor it all to using PreparedStatement#setObject() inside a loop as demonstrated in the utility method below: public static void setValues(PreparedStatement preparedStatement, Object... values) throws SQLException { for (int i = 0; i < values.length; i++) { preparedStatement.setObject(i + 1, values[i]); } } Which can be used as below: preparedStatement = connection.prepareStatement("INSERT INTO Person (name, email, birthdate, photo) VALUES (?, ?, ?, ?)"); setValues(preparedStatement, person.getName(), person.getEmail(), new Timestamp(person.getBirthdate().getTime()), person.getPhoto()); preparedStatement.executeUpdate();

PreparedStatement是一种非常好的防御(但不是万无一失的)，可以防止SQL注入攻击。绑定参数值是防止“小Bobby表”进行不必要访问的好方法。

我遵循了这个问题的所有答案，使用- Statement(但有SQL注入)将工作的遗留代码更改为使用PreparedStatement的解决方案，由于对Statement周围的语义理解不佳，代码要慢得多。addBatch(String sql) & PreparedStatement.addBatch()。

所以我在这里列出了我的情况，这样其他人就不会犯同样的错误。

我的设想是

Statement statement = connection.createStatement();

for (Object object : objectList) {
    //Create a query which would be different for each object 
    // Add this query to statement for batch using - statement.addBatch(query);
}
statement.executeBatch();

所以在上面的代码中，我有数千个不同的查询，都添加到相同的语句中，这段代码工作得更快，因为语句没有被缓存是好的&这段代码很少在应用程序中执行。

现在修复SQL注入，我把这段代码改为，

List<PreparedStatement> pStatements = new ArrayList<>();    
for (Object object : objectList) {
    //Create a query which would be different for each object 
    PreparedStatement pStatement =connection.prepareStatement(query);
    // This query can't be added to batch because its a different query so I used list. 
    //Set parameter to pStatement using object 
    pStatements.add(pStatement);
}// Object loop
// In place of statement.executeBatch(); , I had to loop around the list & execute each update separately          
for (PreparedStatement ps : pStatements) {
    ps.executeUpdate();
}

所以你看，我开始创建数千个PreparedStatement对象，然后最终不能利用批处理，因为我的场景要求-有数千个UPDATE或INSERT查询，所有这些查询碰巧是不同的。

在不降低性能的情况下修复SQL注入是强制性的，我认为在这种情况下使用PreparedStatement是不可能的。

另外，当你使用内置的批处理工具时，你必须担心只关闭一个语句，但使用这个List方法，你需要在重用之前关闭语句，重用一个PreparedStatement

PreparedStatement相对于Statement的一些好处是:

PreparedStatement helps us in preventing SQL injection attacks because it automatically escapes the special characters. PreparedStatement allows us to execute dynamic queries with parameter inputs. PreparedStatement provides different types of setter methods to set the input parameters for the query. PreparedStatement is faster than Statement. It becomes more visible when we reuse the PreparedStatement or use it’s batch processing methods for executing multiple queries. PreparedStatement helps us in writing object Oriented code with setter methods whereas with Statement we have to use String Concatenation to create the query. If there are multiple parameters to set, writing Query using String concatenation looks very ugly and error prone.

阅读更多关于SQL注入问题，请访问http://www.journaldev.com/2489/jdbc-statement-vs-preparedstatement-sql-injection-example

这样更容易阅读 您可以轻松地将查询字符串设置为常量