Spring-boot中的Json对象值操作

Question

我有一个示例 json 如下

[{"state":"Completed","mignum":146289,"projectleader":"Eric Lok","productiondate":"Jun 6, 2018","installationtiers":"Windows Server","targetplatform":"Production","apprelated":"UPS Pickup Point Web Application","appversion":"2.25"},
{"state":"Completed","mignum":146381,"projectleader":"James Rice","productiondate":"Jun 6, 2018","installationtiers":"Linux Web WL10","targetplatform":"Production","apprelated":"Content Only","appversion":""},
{"state":"Pending Migration to Production","mignum":146461,"projectleader":"Nishith Jani","productiondate":"Jun 6, 2018","installationtiers":"Linux BEA WL12","targetplatform":"Production","apprelated":"Tracking Comp","appversion":"1801.20"},
{"state":"Completed","mignum":146574,"projectleader":"Nishith Jani","productiondate":"Jun 6, 2018","installationtiers":"Linux BEA WL12","targetplatform":"Production","apprelated":"Tracking Comp","appversion":"01-00-07-17"}
{"state":Pending Approval by Development in Windward","mignum":146289,"projectleader":"Eric Lok","productiondate":"Jun 6, 2018","installationtiers":"Windows Server","targetplatform":"Production","apprelated":"UPS Pickup Point Web Application","appversion":"2.25"},
{"state":"Completed","mignum":146381,"projectleader":"James Rice","productiondate":"Jun 6, 2018","installationtiers":"Linux Web WL10","targetplatform":"Production","apprelated":"Content Only","appversion":""},
{"state":"Pending Approval by Development in Windward","mignum":146461,"projectleader":"Nishith Jani","productiondate":"Jun 6, 2018","installationtiers":"Linux BEA WL12","targetplatform":"Production","apprelated":"Tracking Comp","appversion":"1801.20"},
{"state":"Pending Migration to Production","mignum":146574,"projectleader":"Nishith Jani","productiondate":"Jun 6, 2018","installationtiers":"Linux BEA WL12","targetplatform":"Production","apprelated":"Tracking Comp","appversion":"01-00-07-17"}
]

我在 Spring 中使用 jdbc 连接从 db 获得

@GetMapping("/dashboard")
public String Data() {
    Connection conn = null;
    List<Map<String, Object>> listOfDates = null;
    try {
        Class.forName("com.mysql.jdbc.Driver");
        conn = DriverManager.getConnection(DB_URL, USER, PASS);
        String countQuery = "SELECT migrations.mignum, migration_states.statemigrations.projectleader, migrations.productiondate, migrations.installationtiers, migrations.targetplatform, migrations.apprelated, migrations.appversion FROM migrations, migration_states WHERE migrations.productiondate='2018-07-07";
        QueryRunner queryRunner = new QueryRunner();
        listOfDates = queryRunner.query(conn, countQuery, new MapListHandler());
        conn.close();
    } catch (SQLException se) {
        se.printStackTrace();
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        DbUtils.closeQuietly(conn);
    }
    return new Gson().toJson(listOfDates);
}

我想解析结果并将其保存在另一个json中，如下所示 1. 第一个结果

[
{
"state":"Completed"
"value": [
    {"mignum":146289,"projectleader":"Eric Lok","productiondate":"Jun 6, 2018","installationtiers":"Windows Server","targetplatform":"Production","apprelated":"UPS Pickup Point Web Application","appversion":"2.25"};
    {"mignum":146381,"projectleader":"James Rice","productiondate":"Jun 6, 2018","installationtiers":"Linux Web WL10","targetplatform":"Production","apprelated":"Content Only","appversion":""},
    {"mignum":146381,"projectleader":"James Rice","productiondate":"Jun 6, 2018","installationtiers":"Linux Web WL10","targetplatform":"Production","apprelated":"Content Only","appversion":""}
]
}
{
"state":"Pending Migration to Production"
"value": [
    {"mignum":146461,"projectleader":"Nishith Jani","productiondate":"Jun 6, 2018","installationtiers":"Linux BEA WL12","targetplatform":"Production","apprelated":"Tracking Comp","appversion":"1801.20"}.
    {"mignum":146574,"projectleader":"Nishith Jani","productiondate":"Jun 6, 2018","installationtiers":"Linux BEA WL12","targetplatform":"Production","apprelated":"Trackin Comp","appversion":"01-00-07-17"}
]
}
{
"state":"Pending Approval by Development in Windward"
"value": [
    {"mignum":146461,"projectleader":"Nishith Jani","productiondate":"Jun 6, 2018","installationtiers":"Linux BEA WL12","targetplatform":"Production","apprelated":"Tracking Comp","appversion":"1801.20"}.
    {"mignum":146574,"projectleader":"Nishith Jani","productiondate":"Jun 6, 2018","installationtiers":"Linux BEA WL12","targetplatform":"Production","apprelated":"Trackin Comp","appversion":"01-00-07-17"}
]
}
]

2。第二个结果

[
  { "state":"Completed", "count": "2"},
  { "state":"Pending Migration to Production", "count": "2"},
  { "state":"Pending Approval by Development in Windward", "count": "2"}
]

我是 Java/Spring 方面这种 json 操作的新手，所以任何人都可以帮助我，因为我很长时间都被困在这一点上

Answer 1

与使用普通 JDBC 相比，使用 JPA（+ Spring Data）可能更有趣，因为这允许您使用类/对象而不是映射，例如：

@Entity
@Table(name = "migrations")
public class Migration {
    @Id
    private Long mignum;
    private LocalDate productiondate;
    private String installationtiers;
    private String targetplatform;
    private String apprelated;
    private String appversion;
    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "mignum")
    private MigrationState state;

    // Getters + Setters
}

@Entity
@Table(name = "migration_states")
public class MigrationState {
    @Id
    private Long mignum;
    private String state;
    private String projectleader;

    // Getters + Setters
}

要进行查询，您可以创建存储库并使用 JPQL：

public interface MigrationRepository extends JpaRepository<Migration, Long> {
    List<Migration> findByProductiondate(LocalDate productiondate);
}

这些类（Migration 和 MigrationState）代表您的数据库模型。由于您的问题不包含所有与数据库相关的信息（仅包含您编写的查询），因此您的情况可能会略有不同。

注意：您实际上并不需要 JPA，这个答案的大部分也可以在没有 JPA 的情况下使用，但是您必须在 Map<String, Object> 和 Migration 之间进行映射自己一个人。

但是，除了这些类之外，您还需要代表您喜欢的输出的类。例如，这适用于您的第二个输出：

public class SimpleStateSummaryDTO {
    private String state;
    private int count;
}

这将适用于您的第一个输出：

public class StateSummaryDTO {
    private String state;
    private List<MigrationDTO> value;

    // Getters + Setters
}

与其使用代表数据库的Migration 类，不如创建一个新类来代表JSON 中的迁移，我们可以称之为MigrationDTO：

public class MigrationDTO {
    private Long mignum;
    private String projectleader;
    private LocalDate productiondate;
    private String installationtiers;
    private String targetplatform;
    private String apprelated;
    private String appversion;

    // Getters + Setters
}

注意：一个DTO代表Data Ttransfer Object，代表数据是用于两个进程之间的通信，在你的情况下是你的 API 和你的消费者。

现在您有了这些类，您可以使用 Java 8 函数式 API 按其状态对 Migration 类进行分组，例如：

repository
    .findByProductiondate(LocalDate.of(2018, 6, 6)).stream()
    .collect(Collectors.groupingBy(migration -> migration.getState().getState()))

但是，这将返回 Map<String, List<Migration>>，这不是您想要的。现在您可以编写自己的收集器，也可以再次流式传输此映射，以便将其映射到您需要的位置。

例如，对于第二个输出将变为：

repository
    .findByProductiondate(LocalDate.of(2018, 6, 6)).stream()
    .collect(Collectors.groupingBy(migration -> migration.getState().getState()))
    .entrySet().stream()
    .map(entry -> new SimpleStateSummaryDTO(entry.getKey(), entry.getValue().size()))
    .collect(Collectors.toList());

我们在这里所做的是，对于每个 Map.Entry<String, List<Migration>>，我们正在创建一个新的 SimpleStateSummaryDTO，其中包含列表的状态和大小。

另一方面，第一个输出需要Migration 到MigrationDTO 的额外映射：

repository
    .findByProductiondate(LocalDate.of(2018, 6, 6)).stream()
    .collect(Collectors.groupingBy(migration -> migration.getState().getState()))
    .entrySet().stream()
    .map(entry -> new StateSummaryDTO(
        entry.getKey(),
        entry.getValue().stream()
            .map(migration -> new MigrationDTO(
                migration.getMignum(),
                migration.getState().getProjectleader(),
                migration.getProductiondate(),
                migration.getInstallationtiers(),
                migration.getTargetplatform(),
                migration.getApprelated(),
                migration.getAppversion()))
        .collect(Collectors.toList())))
.collect(Collectors.toList());

注意：您不需要 Java 8 函数式 API，您可以使用循环编写一些传统逻辑。这只是让它更容易一些。

现在您已经将所需的输出作为对象，您已经完成了很多，因为 Spring 会使用 Jackson 自动将对象转换为 JSON，例如：

@GetMapping
public List<SimpleStateSummaryDTO> findSimple() {
    return repository
        .findByProductiondate(LocalDate.of(2018, 6, 6)).stream()
        .collect(Collectors.groupingBy(migration -> migration.getState().getState()))
        .entrySet().stream()
        .map(entry -> new SimpleStateSummaryDTO(entry.getKey(), entry.getValue().size()))
        .collect(Collectors.toList());
}