如何使用 JDBC PreparedStatement将值列表动态添加到 IN 子句

在本文中，我们将讨论如何使用 JDBC PreparedStatement将值列表动态添加到 IN 子句。

考虑我们在数据库中有一个用户表，而数据库用户表中的记录很少。让我们创建一个用户ID列表并使用StringBuilder动态创建一个 SQL 语句。

下面的代码创建一个带有多个占位符的动态 SQL 查询？在 IN 子句中：

private static String createQuery(int length) {
    String query = "select id, name from users where id in (";
    StringBuilder queryBuilder = new StringBuilder(query);
    for (int i = 0; i < length; i++) {
        queryBuilder.append(" ?");
        if (i != length - 1)
            queryBuilder.append(",");
    }
    queryBuilder.append(")");
    return queryBuilder.toString();
}

带有 IN 子句中参数列表的 JDBC PreparedStatement 示例

package com.javaguides.jdbc.preparestatement.examples;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/**
 * JDBC PreparedStatement with list of parameters in a IN clause Example
 * @author Ramesh Fadatare
 *
 */
public class JDBCPreparedStatementDynamic {

    public static void main(String[] args) {
        List < Integer > ids = new ArrayList < > ();
        ids.add(1);
        ids.add(2);
        ids.add(3);
        ids.add(4);
        processDynamicQuery(ids);

    }
    public static void processDynamicQuery(List < Integer > ids) {

        String query = createQuery(ids.size());

        System.out.println("Query=" + query);
        try (Connection connection = DriverManager
            .getConnection("jdbc:mysql://localhost:3306/mysql_database?useSSL=false", "root", "root");

            // Step 2:Create a statement using connection object
            PreparedStatement preparedStatement = connection.prepareStatement(query)) {
            ResultSet rs = null;

            int parameterIndex = 1;
            for (Iterator < Integer > iterator = ids.iterator(); iterator.hasNext();) {
                Integer id = (Integer) iterator.next();
                preparedStatement.setInt(parameterIndex++, id);
            }
            System.out.println(preparedStatement);
            rs = preparedStatement.executeQuery();
            while (rs.next()) {
                System.out.println("User ID=" + rs.getInt("id") + ", Name=" + rs.getString("name"));
            }

            // close the resultset here
            try {
                rs.close();
            } catch (SQLException e) {}

        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    private static String createQuery(int length) {
        String query = "select id, name from users where id in (";
        StringBuilder queryBuilder = new StringBuilder(query);
        for (int i = 0; i < length; i++) {
            queryBuilder.append(" ?");
            if (i != length - 1)
                queryBuilder.append(",");
        }
        queryBuilder.append(")");
        return queryBuilder.toString();
    }
}

输出：

Query=select id, name from users where id in ( ?, ?, ?, ?)
com.mysql.jdbc.JDBC42PreparedStatement@579bb367: select id, name from users where id in ( 1, 2, 3, 4)
User ID=1, Name=A
User ID=2, Name=Pramod
User ID=3, Name=A
User ID=4, Name=B