嵌套MULTISET/ROW转换及JSON模拟引发ClassCastException问题

云上老周

2026-7-29

jOOQ嵌套Multiset子查询类型序列化异常

执行包含子查询的多列查询，且该子查询嵌套在multiset中时，预期结果应匹配指定类型，但实际嵌套结果仍为ArrayList，未正确序列化为目标类型。

问题复现步骤

record Tuple2(String t1, String t2) {}

var result = db.select(
    multiset(
        select(
            row(
                multiset(
                    select(
                        row("Hello", "World").mapping(Tuple2::new)
                    ).from(dual())
                ).convertFrom(r -> r.map(Record1::component1))
            ).mapping(r -> r)
        ).from(dual())
    ).convertFrom(r -> r.map(Record1::component1))
).from(dual())
.fetchOne(Record1::component1);

log.debug("The result: {}", result);
log.debug("The tuple: {}", result.get(0).get(0));
log.debug("The type of the result: {}", result.get(0).get(0).getClass());

预期result类型为List<List<Tuple2>>，实际却为ArrayList<ArrayList<ArrayList>>（推测是row类型的原始表示）。

代码输出

The result: [[[[Hello, World]]]]
The tuple: [[Hello, World]]
An unhandled error occurred
java.lang.ClassCastException: class java.util.ArrayList cannot be cast to class com.mycompany.mypackage.MyClass$1Tuple2 (java.util.ArrayList is in module java.base of loader 'bootstrap'; com.mycompany.mypackage.MyClass$1Tuple2 is in unnamed module of loader 'app')