Selectively Patch Data with Jackson ObjectMapper in Spring Web & Spring Data

README.md

Selectively Patch Data with Jackson ObjectMapper in Spring Web & Spring Data

Although this is done in Spring, the feature is provided by Jackson ObjectMapper.

Libraries used in this example

• com.fasterxml.jackson.core:jackson-databind
• org.springframework.boot:spring-boot-starter-web
• org.springframework.boot:spring-boot-starter-json
• org.springframework.boot:spring-boot-starter-validation
• org.springframework.boot:spring-boot-starter-data-jpa

Data.java

@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonIgnoreProperties(ignoreUnknown = true)
@Entity
public class Data {

    @NotNull
    @Id
    @Column(length = 255, updatable = false, nullable = false, unique = true)
    private String id;

    @NotNull
    @ManyToOne(fetch = FetchType.EAGER, cascade = {})
    private User user;

    @NotBlank
    @Length(max = 255)
    @Column(length = 255, updatable = true, nullable = false, unique = false)
    private String title;

    @Length(max = 2500)
    @Column(length = 2500, updatable = true, nullable = true, unique = false)
    private String content;

    public Record() {
    }

    public Record(@NotNull String id, @NotNull User user, @NotBlank @Length(max = 255) String title, @Length(max = 2500) String content) {
        this.id = id;
        this.user = user;
        this.title = title;
        this.content = content;
    }

    @PrePersist
    void prePersist() {
        id = UUID.randomUUID().toString();
    }

    public String getId() {
        return id;
    }

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }
}

DataController.java

@RestController
@RequestMapping("/data")
public class DataController implements PatchController {

    private final DataRepository repository;

    public DataController(DataRepository repository) {
        this.repository = repository;
    }
    
    /**
     * @return Record or {@code null}
     */
    @GetMapping("/{id}")
    public Data get(@PathVariable("id") String id) {
        return repository.findById(id)
                .orElse(null);
    }

    @PatchMapping("/{id}")
    public Data patch(@PathVariable("id") String id, @RequestBody DataPatch patch) {
        return repository.findById(id)
                .map(Data -> {
                    Data = patch(Data, patch);
                    return repository.save(Data);
                })
                .orElseThrow(ForbiddenException::new);
    }
}

DataPatch.java

@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonIgnoreProperties(ignoreUnknown = true)
public class DataPatch {
    public String title;
    public String content;
}

PatchController.java

public interface PatchController {
    ObjectMapper objectMapper = new ObjectMapper();

    default <Data, Patch> Data patch(Data data, Patch patch) throws JsonException {
        ObjectReader objectReader = objectMapper.readerForUpdating(data);

        JsonNode patchNode = objectMapper.valueToTree(patch);
        try {
            return objectReader.readValue(patchNode);
        } catch (IOException e) {
            throw new JsonException(e);
        }
    }
}