PagerResult

json.java

String inputJson = """
            {
              "b": 2,
              "a": {
                "x": 10,
                "y": [1, 2, 3]
              }
            }
            """;

        ObjectMapper mapper = new ObjectMapper();

        // Read as generic tree (schema agnostic)
        JsonNode node = mapper.readTree(inputJson);

        // Ensure compact output (no indentation, no newlines)
        mapper.disable(SerializationFeature.INDENT_OUTPUT);

        String compactJson = mapper.writeValueAsString(node);

        System.out.println(compactJson);

PagerResult.java

import java.net.URI;
import java.util.List;
import java.util.Map;
import java.util.Objects;

public record PagedResult<T>(
        List<T> content,
        int pageNumber,      // 1-based
        int pageSize,
        long totalElements,
        int totalPages,
        Map<LinkRelation, URI> links
) {

    public PagedResult {
        Objects.requireNonNull(content, "content must not be null");
        Objects.requireNonNull(links, "links must not be null");

        if (pageNumber < 1)
            throw new IllegalArgumentException("pageNumber must be >= 1");

        if (pageSize <= 0)
            throw new IllegalArgumentException("pageSize must be > 0");

        if (totalElements < 0)
            throw new IllegalArgumentException("totalElements must be >= 0");

        int calculatedTotalPages = calculateTotalPages(totalElements, pageSize);

        if (totalPages != calculatedTotalPages)
            throw new IllegalArgumentException(
                    "totalPages must equal calculated value: " + calculatedTotalPages
            );

        if (totalPages > 0 && pageNumber > totalPages)
            throw new IllegalArgumentException("pageNumber cannot exceed totalPages");

        // Defensive copies for immutability
        content = List.copyOf(content);
        links = Map.copyOf(links);
    }

    private static int calculateTotalPages(long totalElements, int pageSize) {
        if (totalElements == 0) {
            return 0;
        }
        return (int) Math.ceil((double) totalElements / pageSize);
    }

    public boolean hasNext() {
        return pageNumber < totalPages;
    }

    public boolean hasPrevious() {
        return pageNumber > 1;
    }

    public enum LinkRelation {
        SELF,
        FIRST,
        PREVIOUS,
        NEXT,
        LAST
    }
}


PagedResult<String> result = new PagedResult<>(
        List.of("A", "B", "C"),
        2,
        3,
        10,
        4,
        Map.of(
            PagedResult.LinkRelation.SELF, URI.create("/items?page=2"),
            PagedResult.LinkRelation.NEXT, URI.create("/items?page=3"),
            PagedResult.LinkRelation.PREVIOUS, URI.create("/items?page=1")
        )
);