在java.sql实例中使用SQL IN子句的最佳变通方法是什么?由于SQL注入攻击安全问题,不支持多值的PreparedStatement:一个?占位符表示一个值,而不是一个值列表。

考虑下面的SQL语句:

SELECT my_column FROM my_table where search_column IN (?)

使用preparedStatement。setString(1, "'A', 'B', 'C'");本质上是一种无用的尝试,试图解决使用原因?首先。

有什么可行的解决办法?


当前回答

我只是为此制定了一个特定于postgresql的选项。它有点像黑客,有自己的优缺点和局限性,但它似乎是有效的,而且不局限于特定的开发语言、平台或PG驱动程序。

当然,诀窍是找到一种方法,将任意长度的值集合作为单个参数传递,并让db将其识别为多个值。我的解决方案是从集合中的值构造一个带分隔符的字符串,将该字符串作为单个参数传递,并使用string_to_array()与PostgreSQL正确使用它所需的强制转换。

因此,如果你想搜索“foo”,“blah”和“abc”,你可以将它们连接成一个字符串,如:'foo,blah,abc'。下面是直接的SQL语句:

select column from table
where search_column = any (string_to_array('foo,blah,abc', ',')::text[]);

显然,您可以将显式强制转换更改为您想要的结果值数组——int、text、uuid等。因为函数接受一个字符串值(或者两个,如果你也想自定义分隔符),你可以在准备好的语句中作为参数传递它:

select column from table
where search_column = any (string_to_array($1, ',')::text[]);

这甚至足够灵活,可以支持like比较:

select column from table
where search_column like any (string_to_array('foo%,blah%,abc%', ',')::text[]);

Again, no question it's a hack, but it works and allows you to still use pre-compiled prepared statements that take *ahem* discrete parameters, with the accompanying security and (maybe) performance benefits. Is it advisable and actually performant? Naturally, it depends, as you've got string parsing and possibly casting going on before your query even runs. If you're expecting to send three, five, a few dozen values, sure, it's probably fine. A few thousand? Yeah, maybe not so much. YMMV, limitations and exclusions apply, no warranty express or implied.

但它确实有效。

其他回答

我认为您可以(使用基本的字符串操作)在PreparedStatement中生成查询字符串,使其具有与列表中项的数量相匹配的若干?

当然,如果你这样做,你只是一个步骤,生成一个巨大的链或在你的查询,但没有正确的数字?在查询字符串中,我不知道你还能如何解决这个问题。

PreparedStatement没有提供任何处理SQL IN子句的好方法。根据http://www.javaranch.com/journal/200510/Journal200510.jsp#a2“你不能替代那些意味着成为SQL语句一部分的东西。这是必要的,因为如果SQL本身可以更改,驱动程序就不能预编译语句。它还具有防止SQL注入攻击的良好副作用。”我最终使用了以下方法:

String query = "SELECT my_column FROM my_table where search_column IN ($searchColumns)";
query = query.replace("$searchColumns", "'A', 'B', 'C'");
Statement stmt = connection.createStatement();
boolean hasResults = stmt.execute(query);
do {
    if (hasResults)
        return stmt.getResultSet();

    hasResults = stmt.getMoreResults();

} while (hasResults || stmt.getUpdateCount() != -1);

Spring允许将java.util.Lists传递给NamedParameterJdbcTemplate,这将自动生成(?, ?, ?,…, ?),作为适当的参数数量。

对于Oracle,这篇博文讨论了Oracle .sql. array (Connection. array)的使用。createArrayOf不支持Oracle)。为此你必须修改你的SQL语句:

SELECT my_column FROM my_table where search_column IN (select COLUMN_VALUE from table(?))

oracle table函数将传递的数组转换为在in语句中可用的类似表的值。

下面是一个完整的Java解决方案来为你创建准备好的语句:

/*usage:

Util u = new Util(500); //500 items per bracket. 
String sqlBefore  = "select * from myTable where (";
List<Integer> values = new ArrayList<Integer>(Arrays.asList(1,2,4,5)); 
string sqlAfter = ") and foo = 'bar'"; 

PreparedStatement ps = u.prepareStatements(sqlBefore, values, sqlAfter, connection, "someId");
*/



import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class Util {

    private int numValuesInClause;

    public Util(int numValuesInClause) {
        super();
        this.numValuesInClause = numValuesInClause;
    }

    public int getNumValuesInClause() {
        return numValuesInClause;
    }

    public void setNumValuesInClause(int numValuesInClause) {
        this.numValuesInClause = numValuesInClause;
    }

    /** Split a given list into a list of lists for the given size of numValuesInClause*/
    public List<List<Integer>> splitList(
            List<Integer> values) {


        List<List<Integer>> newList = new ArrayList<List<Integer>>(); 
        while (values.size() > numValuesInClause) {
            List<Integer> sublist = values.subList(0,numValuesInClause);
            List<Integer> values2 = values.subList(numValuesInClause, values.size());   
            values = values2; 

            newList.add( sublist);
        }
        newList.add(values);

        return newList;
    }

    /**
     * Generates a series of split out in clause statements. 
     * @param sqlBefore ""select * from dual where ("
     * @param values [1,2,3,4,5,6,7,8,9,10]
     * @param "sqlAfter ) and id = 5"
     * @return "select * from dual where (id in (1,2,3) or id in (4,5,6) or id in (7,8,9) or id in (10)"
     */
    public String genInClauseSql(String sqlBefore, List<Integer> values,
            String sqlAfter, String identifier) 
    {
        List<List<Integer>> newLists = splitList(values);
        String stmt = sqlBefore;

        /* now generate the in clause for each list */
        int j = 0; /* keep track of list:newLists index */
        for (List<Integer> list : newLists) {
            stmt = stmt + identifier +" in (";
            StringBuilder innerBuilder = new StringBuilder();

            for (int i = 0; i < list.size(); i++) {
                innerBuilder.append("?,");
            }



            String inClause = innerBuilder.deleteCharAt(
                    innerBuilder.length() - 1).toString();

            stmt = stmt + inClause;
            stmt = stmt + ")";


            if (++j < newLists.size()) {
                stmt = stmt + " OR ";
            }

        }

        stmt = stmt + sqlAfter;
        return stmt;
    }

    /**
     * Method to convert your SQL and a list of ID into a safe prepared
     * statements
     * 
     * @throws SQLException
     */
    public PreparedStatement prepareStatements(String sqlBefore,
            ArrayList<Integer> values, String sqlAfter, Connection c, String identifier)
            throws SQLException {

        /* First split our potentially big list into lots of lists */
        String stmt = genInClauseSql(sqlBefore, values, sqlAfter, identifier);
        PreparedStatement ps = c.prepareStatement(stmt);

        int i = 1;
        for (int val : values)
        {

            ps.setInt(i++, val);

        }
        return ps;

    }

}

Sormula支持SQL IN操作符,它允许你提供一个java.util.Collection对象作为参数。它使用?对于集合中的每个元素。参见示例4(示例中的SQL是一个注释,用于澄清Sormula创建但不使用的内容)。