Snippet

Custom Delimited Array Binding with Generic StringToCollectionConverter

Spring's Converter SPI converts raw HTTP request parameters directly into typed arrays or custom objects. Implementing Converter<String, Integer[]> registers an automatic binding mechanism for semicolon-delimited query parameters without requiring repetitive string splitting across multiple controller methods.

snippet.java

java

@Component
public class DelimitedIntegerArrayConverter implements Converter<String, Integer[]> {
 
    @Override
    public Integer[] convert(String source) {
        if (source == null || source.isBlank()) {
            return new Integer[0];
        }
        return Arrays.stream(source.split(";"))
            .map(String::trim)
            .filter(Predicate.not(String::isEmpty))
            .map(Integer::valueOf)
            .toArray(Integer[]::new);
    }
}
 
@RestController
@RequestMapping("/api/metrics")
public class MetricsController {
 
    @GetMapping
    public ResponseEntity<Integer> sumMetricIds(@RequestParam("ids") Integer[] metricIds) {
        int total = Arrays.stream(metricIds).mapToInt(Integer::intValue).sum();
        return ResponseEntity.ok(total);
    }
}

spring

Breakdown

public class DelimitedIntegerArrayConverter implements Converter<String, Integer[]>

Defines a custom type-conversion strategy registered within Spring's core conversion service.

.toArray(Integer[]::new);

Constructs a typed primitive wrapper array from the intermediate stream elements using a constructor reference.

public ResponseEntity<Integer> sumMetricIds(@RequestParam("ids") Integer[] metricIds)

The controller receives a ready-to-use Integer array parsed directly from a delimited request parameter string.

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Custom Delimited Array Binding with Generic StringToCollectionConverter

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