Spring中用JsonView过滤数据输出

文章目錄

1. 1. 翻译原文链接 Latest Jackson integration improvements in Spring

这篇文章将会讲述如何使用@JsonView过滤给前台数据的输出在序列化的上下文中，包括集合和单字段。

翻译原文链接 Latest Jackson integration improvements in Spring

例子

这个例子中我们将会用”summary” View 来标志被序列化的字段。

public class View {
	interface Summary {}
}

public class User {

	@JsonView(View.Summary.class)
	private Long id;

	@JsonView(View.Summary.class)
	private String firstname;

	@JsonView(View.Summary.class)
	private String lastname;

	private String email;
	private String address;
	private String postalCode;
	private String city;
	private String country;
}

public class Message {

	@JsonView(View.Summary.class)
	private Long id;

	@JsonView(View.Summary.class)
	private LocalDate created;

	@JsonView(View.Summary.class)
	private String title;

	@JsonView(View.Summary.class)
	private User author;

	private List<User> recipients;
  
	private String body;
}

@JsonView这个注解应用非常灵活。这个注解我们可以加在一个Controlelr的方法上，这个方法的返回的类中的字段就会被@JsonView序列化。

@RestController
public class MessageController {

	@Autowired
	private MessageService messageService;

	@JsonView(View.Summary.class)
	@RequestMapping("/")
	public List<Message> getAllMessages() {
		return messageService.getAll();
	}

	@RequestMapping("/{id}")
	public Message getMessage(@PathVariable Long id) {
		return messageService.get(id);
	}
}

看这段代码我们知道，getAllMessages()方法是retrieved所有的message,但是返回的时侯每个类中只会返回我们加@JsonView注解的字段。

[ {
  "id" : 1,
  "created" : "2014-11-14",
  "title" : "Info",
  "author" : {
    "id" : 1,
    "firstname" : "Brian",
    "lastname" : "Clozel"
  }
}, {
  "id" : 2,
  "created" : "2014-11-14",
  "title" : "Warning",
  "author" : {
    "id" : 2,
    "firstname" : "Stéphane",
    "lastname" : "Nicoll"
  }
}, {
  "id" : 3,
  "created" : "2014-11-14",
  "title" : "Alert",
  "author" : {
    "id" : 3,
    "firstname" : "Rossen",
    "lastname" : "Stoyanchev"
  }
} ]

在Spring MVC的default configuration，MapperFeature.DEFAULT_VIEW_INCLUSION是为false，这意味着，当我们使用JSON View的时候，没有被注解的fields or properties body recipients将不会被序列化。

当然，当我们使用getMessage()retrieved一个明确的message的时候，因为方法中没有使用JSON View,所以所有的字段将被序列化。

{
  "id" : 1,
  "created" : "2014-11-14",
  "title" : "Info",
  "body" : "This is an information message",
  "author" : {
    "id" : 1,
    "firstname" : "Brian",
    "lastname" : "Clozel",
    "email" : "bclozel@pivotal.io",
    "address" : "1 Jaures street",
    "postalCode" : "69003",
    "city" : "Lyon",
    "country" : "France"
  },
  "recipients" : [ {
    "id" : 2,
    "firstname" : "Stéphane",
    "lastname" : "Nicoll",
    "email" : "snicoll@pivotal.io",
    "address" : "42 Obama street",
    "postalCode" : "1000",
    "city" : "Brussel",
    "country" : "Belgium"
  }, {
    "id" : 3,
    "firstname" : "Rossen",
    "lastname" : "Stoyanchev",
    "email" : "rstoyanchev@pivotal.io",
    "address" : "3 Warren street",
    "postalCode" : "10011",
    "city" : "New York",
    "country" : "USA"
  } ]
}

一个类或接口可以使用@JsonView，但是有的时候我们会经常遇到@OneToMany or @ManyToMany，但是我么可以用继承来解决集合或List的问题。例如，在这个例子中我们会看到private List<User> recipients;，我们用的注解不是@JsonView(View.Summary.class)而是继承他的注解@JsonView(View.SummaryWithRecipients.class)来完成，在下面的这个方法中的字段将会被@JsonView(View.Summary.class) 和 @JsonView(View.SummaryWithRecipients.class) 共同序列化。

public class View {
	interface Summary {}
	interface SummaryWithRecipients extends Summary {}
}

public class Message {

	@JsonView(View.Summary.class)
	private Long id;

	@JsonView(View.Summary.class)
	private LocalDate created;

	@JsonView(View.Summary.class)
	private String title;

	@JsonView(View.Summary.class)
	private User author;

	@JsonView(View.SummaryWithRecipients.class)
	private List<User> recipients;
  
	private String body;
}

@RestController
public class MessageController {

	@Autowired
	private MessageService messageService;

	@JsonView(View.SummaryWithRecipients.class)
	@RequestMapping("/with-recipients")
	public List<Message> getAllMessagesWithRecipients() {
		return messageService.getAll();
	}
}