對於每個開發web的人來說,JSON肯定都不陌生.它的輕量級與簡潔性,使得它備受青睞.同時,隨着前後臺技術的不斷成熟,Json解析技術也發展地越來越完善.在這衆多的Json解析技術中,備受歡迎的則是我們今天要講的以下三種:
Jackson
Gson
json-b
1.jackson
Jackson是一個簡單基於Java應用庫,Jackson可以輕鬆的將Java對象轉換成json對象和xml文檔,同樣也可以將json、xml轉換成Java對象。Jackson所依賴的jar包較少,簡單易用並且性能也要相對高些,並且Jackson社區相對比較活躍,更新速度也比較快。從SpringMVC到SpringBoot,官方推薦的都是jackson.,它主要具備以下幾個優點:容易使用。
容易使用 - jackson API提供了一個高層次外觀,以簡化常用的用例。
無需創建映射 - API提供了默認的映射大部分對象序列化。
性能高 - 快速,低內存佔用,適合大型對象圖表或系統。
乾淨的JSON - jackson創建一個乾淨和緊湊的JSON結果,這是讓人很容易閱讀。
不依賴 - 庫不需要任何其他的庫,除了JDK。
開源代碼 - jackson是開源的,可以免費使用。
1.1 jackson的常規使用
對於我們而言,我們比較關心的是他的序列化操作,這裏我們先引入jackson的依賴包
<dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> </dependency>
構建成功後,我們看到依賴裏出現了:
jackson-annotations-2.9.0.jar jackson-core-2.9.7.jar jackson-databind-2.9.7.jar
這是jackson的依賴庫,接下來我們創建一個基本的實體類:
package top.lianmengtu.testjson.domain; import lombok.Getter; import lombok.Setter; @Getter @Setter public class UserInfo { private Long id; private String nickName; private Boolean gender; }
我們來一個測試類:
package top.lianmengtu.testjson; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import top.lianmengtu.testjson.domain.UserInfo; public class MyJsonTest { public static void main(String[] args) { ObjectMapper objectMapper=new ObjectMapper(); UserInfo userInfo = new UserInfo(); userInfo.setId(1l); userInfo.setNickName("Nick"); userInfo.setGender(false); String userInfoString= null; try { userInfoString = objectMapper.writeValueAsString(userInfo); } catch (JsonProcessingException e) { e.printStackTrace(); } System.out.println(userInfoString); } }
運行結果如下:
{"id":1,"nickName":"Nick","gender":false}
這是一個基本類型,我們這裏添加兩個屬性,一個基本類型的List,另一個是日期類型:
package top.lianmengtu.testjson.domain; import com.fasterxml.jackson.annotation.JsonFormat; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import lombok.Getter; import lombok.Setter; import java.util.ArrayList; import java.util.Date; import java.util.List; @Getter @Setter public class UserInfo { private Long id; private String nickName; private Boolean gender; private List<String> roleList; private Date createTime; }
測試類如下:
package top.lianmengtu.testjson; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import top.lianmengtu.testjson.domain.UserInfo; import java.util.ArrayList; import java.util.Date; import java.util.List; public class MyJsonTest { public static void main(String[] args) { ObjectMapper objectMapper =new ObjectMapper(); UserInfo userInfo = new UserInfo(); userInfo.setId(1l); userInfo.setNickName("Nick"); userInfo.setGender(false); List<String> roleList=new ArrayList<>(); roleList.add("admin"); roleList.add("manager"); userInfo.setRoleList(roleList); userInfo.setCreateTime(new Date()); String userInfoString= null; try { userInfoString = objectMapper.writeValueAsString(userInfo); } catch (JsonProcessingException e) { e.printStackTrace(); } System.out.println(userInfoString); } }
運行結果如下:
{"id":1,"nickName":"Nick","gender":false,"roleList":["admin","manager"],"createTime":1540451548817}
這裏我們看到基本類型的List按着我們的期望解析了,但日期明顯不是我們想要的,這裏我們可以使用@JsonFormat來傳入我們想要的格式,如下所示:
package top.lianmengtu.testjson.domain; import com.fasterxml.jackson.annotation.JsonFormat; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import lombok.Getter; import lombok.Setter; import java.util.ArrayList; import java.util.Date; import java.util.List; @Getter @Setter public class UserInfo { private Long id; private String nickName; private Boolean gender; private List<String> roleList; @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss") private Date createTime; }
這裏我們的測試類不變,運行結果如下所示:
{"id":1,"nickName":"Nick","gender":false,"roleList":["admin","manager"],"createTime":"2018-10-25 07:16:12"}
此時,我們看到日期類型已經按着我們期望的格式進行展示了.我們在使用的時候,常會使用內嵌類型,這裏我們給用戶定義一個公司:
package top.lianmengtu.testjson.domain; import lombok.Getter; import lombok.Setter; @Setter @Getter public class Company { private Long id; private String name; private String address; }
我們再給用戶定義一個公司列表,表明用戶工作過的公司:
package top.lianmengtu.testjson.domain; import com.fasterxml.jackson.annotation.JsonFormat; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import lombok.Getter; import lombok.Setter; import java.util.ArrayList; import java.util.Date; import java.util.List; @Getter @Setter public class UserInfo { private Long id; private String nickName; private Boolean gender; private List<String> roleList; private List<Company> companies; @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss") private Date createTime; }
我們也修改一下測試類:
package top.lianmengtu.testjson; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import top.lianmengtu.testjson.domain.Company; import top.lianmengtu.testjson.domain.UserInfo; import java.util.ArrayList; import java.util.Date; import java.util.List; public class MyJsonTest { public static void main(String[] args) { ObjectMapper objectMapper =new ObjectMapper(); UserInfo userInfo = new UserInfo(); userInfo.setId(1l); userInfo.setNickName("Nick"); userInfo.setGender(false); List<String> roleList=new ArrayList<>(); roleList.add("admin"); roleList.add("manager"); userInfo.setRoleList(roleList); Company baidu=new Company(); baidu.setId(1l); baidu.setName("百度"); baidu.setAddress("西二旗"); List<Company> companies = new ArrayList<>(); companies.add(baidu); userInfo.setCompanies(companies); userInfo.setCreateTime(new Date()); String userInfoString= null; try { userInfoString = objectMapper.writeValueAsString(userInfo); } catch (JsonProcessingException e) { e.printStackTrace(); } System.out.println(userInfoString); } }
運行結果如下:
{"id":1,"nickName":"Nick","gender":false,"roleList":["admin","manager"],"companies":[{"id":1,"name":"百度","address":"西二旗"}],"createTime":"2018-10-25 07:19:42"}
1.2 SpringBoot中的jackson
展示了基本使用之後,我們現在來看一下SpringBoot對Jackson的支持,當我們在pom中添加了spring-boot-starter-web 之後,我們發現已經自動加入了jackson的三個包.啓動類如下:
package top.lianmengtu.testjson; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication public class Application { public static void main(String[] args) { SpringApplication.run(Application.class,args); } }
JsonController類代碼如下所示:
package top.lianmengtu.testjson.controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import top.lianmengtu.testjson.domain.Company; import top.lianmengtu.testjson.domain.UserInfo; import java.util.ArrayList; import java.util.Date; import java.util.List; @RestController @RequestMapping("json/") public class JsonController { @RequestMapping("basic_json") public UserInfo basicJson(){ UserInfo userInfo = new UserInfo(); userInfo.setId(1l); userInfo.setNickName("Nick"); userInfo.setGender(false); List<String> roleList=new ArrayList<>(); roleList.add("admin"); roleList.add("manager"); userInfo.setRoleList(roleList); Company baidu=new Company(); baidu.setId(1l); baidu.setName("百度"); baidu.setAddress("西二旗"); List<Company> companies = new ArrayList<>(); companies.add(baidu); userInfo.setCompanies(companies); userInfo.setCreateTime(new Date()); return userInfo; } }
我們啓動項目,然後打開瀏覽器,結果如下所示:
{"id":1,"nickName":"Nick","gender":false,"roleList":["admin","manager"],"companies":[{"id":1,"name":"百度","address":"西二旗"}],"createTime":"2018-10-25 07:44:13"}
和我們剛剛演示的一樣,但現在有兩個問題,首先,包含日期類型的model可能不只一個,如果我們在model裏添加@JsonFormat可能每一個都需要加,比較地繁瑣.其次,有些時候我們可能沒有辦法改變model的源碼,因此不能給諸如日期這樣的字段添加@JsonFormat註解,那怎麼辦呢?此時我們就可以將我們的配置外移,移到application.yml裏,如下所示:
spring: jackson: date-format: 'yyyy-MM-dd'
然後我們將實體類裏的@JsonFormat去掉,如下所示:
package top.lianmengtu.testjson.domain; import com.fasterxml.jackson.annotation.JsonFormat; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import lombok.Getter; import lombok.Setter; import java.util.ArrayList; import java.util.Date; import java.util.List; @Getter @Setter public class UserInfo { private Long id; private String nickName; private Boolean gender; private List<String> roleList; private List<Company> companies; private Date createTime; }
我們運行我們的代碼,發現日期現在變成了我們在配置文件裏配置的yyyy-MM-dd的格式:
{"id":1,"nickName":"Nick","gender":false,"roleList":["admin","manager"],"companies":[{"id":1,"name":"百度","address":"西二旗"}],"createTime":"2018-10-25"}
不過這裏有一點需要說明一下,如果我們即在yml裏進行了配置,同時也使用了@JsonFormat註解,那麼@JsonFormat會覆蓋yml裏的。除此之外,springBoot還支持jackson以下一些屬性的使用:
spring.jackson.default-property-inclusion= spring.jackson.deserialization.*= spring.jackson.generator.*= spring.jackson.joda-date-time-format= spring.jackson.locale= spring.jackson.mapper.*= spring.jackson.parser.*= spring.jackson.property-naming-strategy= spring.jackson.serialization.*= spring.jackson.time-zone=
它使用的方式和objectMapper使用的方式幾乎一模一樣,比如,我們剛剛嘗試過關於日期格式的問題,在我們沒有寫JsonFormat的時候,jackson會自動將我們的日期格式轉換爲時間戳,現在我們來禁用這個屬性
public static void main(String[] args) { ObjectMapper objectMapper=new ObjectMapper(); UserInfo userInfo = new UserInfo(); userInfo.setId(1l); userInfo.setNickName("Nick"); userInfo.setGender(false); userInfo.setCreateTime(new Date()); objectMapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS); String userInfoString= null; try { userInfoString = objectMapper.writeValueAsString(userInfo); } catch (JsonProcessingException e) { e.printStackTrace(); } System.out.println(userInfoString); }
因爲serialization是一個map,所以在yml裏這麼寫
spring: jackson: serialization: /write_dates_as_timestamps: false
當我們禁用之後,打印出來的字符串如下所示:
{"id":1,"nickName":"Nick","gender":false,"roleList":null,"companies":null,"createTime":"2018-10-25T08:46:32.192+0000"}
我們發現,已經不在是時間戳了,說明我們的配置已經生效了,其他的,大家可以進到相應的實現裏去一一查看.
2. gson的使用
gson是google出的一個json解析工具.使用它的時候,我們只需要在pom中添加gson一個包就可以了,如下所示:
<dependency> <groupId>com.google.code.gson</groupId> <artifactId>gson</artifactId> <version>2.8.5</version> </dependency>
2.1 gson的基本使用
我們還是先來看一下gson的基本使用.我們仍然使用剛剛那個實體類:
package top.lianmengtu.testjson.domain; import lombok.Getter; import lombok.Setter; import java.util.Date; import java.util.List; @Getter @Setter public class UserInfo { private Long id; private String nickName; private Boolean gender; private List<String> roleList; private List<Company> companies; private Date createTime; }
然後是我們的測試類:
package top.lianmengtu.testjson; import com.google.gson.Gson; import com.google.gson.GsonBuilder; import com.google.gson.JsonObject; import top.lianmengtu.testjson.domain.Company; import top.lianmengtu.testjson.domain.UserInfo; import java.util.ArrayList; import java.util.Date; import java.util.List; public class GsonTest { public static void main(String[] args) { UserInfo userInfo = new UserInfo(); userInfo.setId(1l); userInfo.setNickName("Nick"); userInfo.setGender(false); List<String> roleList=new ArrayList<>(); roleList.add("admin"); roleList.add("manager"); userInfo.setRoleList(roleList); Company baidu=new Company(); baidu.setId(1l); baidu.setName("百度"); baidu.setAddress("西二旗"); List<Company> companies = new ArrayList<>(); companies.add(baidu); userInfo.setCompanies(companies); userInfo.setCreateTime(new Date()); Gson gson=new Gson(); String userInfoString=gson.toJson(userInfo); System.out.println(userInfoString); } }
然後運行結果如下所示:
{"id":1,"nickName":"Nick","gender":false,"roleList":["admin","manager"],"companies":[{"id":1,"name":"百度","address":"西二旗"}],"createTime":"Oct 25, 2018, 5:12:44 PM"}
現在我們來展示他的日期轉換,在gson中我們處理日期轉換可以使用gsonbuilder去處理,如下所示(因爲重點是日期,所以略過其他字段):
package top.lianmengtu.testjson; import com.google.gson.Gson; import com.google.gson.GsonBuilder; import top.lianmengtu.testjson.domain.UserInfo; import java.util.Date; public class GsonTest { public static void main(String[] args) { UserInfo userInfo = new UserInfo(); userInfo.setCreateTime(new Date()); GsonBuilder gsonBuilder = new GsonBuilder(); gsonBuilder.setDateFormat("yyyy-MM-dd"); Gson gson=gsonBuilder.create(); String userInfoString=gson.toJson(userInfo); System.out.println(userInfoString); } }
測試結果如下所示:
{"createTime":"2018-10-25"}
gsonbuilder的這種處理方式,除了能處理date類型外,還能處理long類型,可以將long轉換爲字符串或者轉換爲數字類型.默認是將long轉換爲數字,這裏我們處理成字符串,測試類如下所示:
package top.lianmengtu.testjson; import com.google.gson.Gson; import com.google.gson.GsonBuilder; import com.google.gson.LongSerializationPolicy; import top.lianmengtu.testjson.domain.UserInfo; import java.util.Date; public class GsonTest { public static void main(String[] args) { UserInfo userInfo = new UserInfo(); userInfo.setId(1l); userInfo.setCreateTime(new Date()); GsonBuilder gsonBuilder = new GsonBuilder(); gsonBuilder.setDateFormat("yyyy-MM-dd"); gsonBuilder.setLongSerializationPolicy(LongSerializationPolicy.STRING); Gson gson=gsonBuilder.create(); String userInfoString=gson.toJson(userInfo); System.out.println(userInfoString); } }
運行結果如下:
{"id":"1","createTime":"2018-10-25"}
之前在json的時候出現過一種情況,就是循環解析導致報錯的,最典型的情況是對tree的解析,之前我們曾在tree裏設置children來存放子節點,同時又設置了parent來存放父節點,後來就直接報錯了.除了這些之外,還有一些純粹是爲了我們的業務邏輯而設置的屬性,這些我們也需要忽略,那gson如何實現這個功能呢:
1.字段上標註transient或@Expose
實體類代碼如下所示:
package top.lianmengtu.testjson.domain; import lombok.Getter; import lombok.Setter; import org.springframework.format.annotation.DateTimeFormat; import java.util.Date; import java.util.List; @Getter @Setter public class UserInfo { private transient Long id; private String nickName; private Boolean gender; private List<String> roleList; private List<Company> companies; private Date createTime; }
然後我們仍然運行上面的測試代碼,運行結果如下所示:
{"createTime":"2018-10-25"}
使用transient是標記需要排除的,而@Expose則標記的是需要序列化的字段.實體類修改如下:
package top.lianmengtu.testjson.domain; import com.google.gson.annotations.Expose; import lombok.Getter; import lombok.Setter; import org.springframework.format.annotation.DateTimeFormat; import java.util.Date; import java.util.List; @Getter @Setter public class UserInfo { @Expose private Long id; @Expose private String nickName; @Expose private Boolean gender; private List<String> roleList; private List<Company> companies; @Expose private Date createTime; }
測試代碼修改如下:
package top.lianmengtu.testjson; import com.google.gson.*; import top.lianmengtu.testjson.domain.Company; import top.lianmengtu.testjson.domain.UserInfo; import java.util.ArrayList; import java.util.Date; import java.util.List; public class GsonTest { public static void main(String[] args) { UserInfo userInfo = new UserInfo(); userInfo.setId(1l); userInfo.setCreateTime(new Date()); userInfo.setNickName("Nick"); userInfo.setGender(false); List<String> roleList=new ArrayList<>(); roleList.add("admin"); roleList.add("manager"); userInfo.setRoleList(roleList); Company baidu=new Company(); baidu.setId(1l); baidu.setName("百度"); baidu.setAddress("西二旗"); List<Company> companies = new ArrayList<>(); companies.add(baidu); userInfo.setCompanies(companies); GsonBuilder gsonBuilder = new GsonBuilder(); gsonBuilder.setDateFormat("yyyy-MM-dd"); gsonBuilder.excludeFieldsWithoutExposeAnnotation(); Gson gson=gsonBuilder.create(); String userInfoString=gson.toJson(userInfo); System.out.println(userInfoString); } }
運行結果如下:
{"id":1,"nickName":"Nick","gender":false,"createTime":"2018-10-25"}
2.使用排除策略 exclusionStrategy
排除策略有很多種,另一種是傳字符串去匹配,測試代碼修改如下:
package top.lianmengtu.testjson; import com.google.gson.*; import top.lianmengtu.testjson.domain.Company; import top.lianmengtu.testjson.domain.UserInfo; import java.util.ArrayList; import java.util.Date; import java.util.List; public class GsonTest { public static void main(String[] args) { UserInfo userInfo = new UserInfo(); userInfo.setId(1l); userInfo.setCreateTime(new Date()); userInfo.setNickName("Nick"); userInfo.setGender(false); List<String> roleList=new ArrayList<>(); roleList.add("admin"); roleList.add("manager"); userInfo.setRoleList(roleList); Company baidu=new Company(); baidu.setId(1l); baidu.setName("百度"); baidu.setAddress("西二旗"); List<Company> companies = new ArrayList<>(); companies.add(baidu); userInfo.setCompanies(companies); GsonBuilder gsonBuilder = new GsonBuilder(); gsonBuilder.setDateFormat("yyyy-MM-dd"); final List<String> filedList= new ArrayList<>(); filedList.add("companies"); filedList.add("nickName"); gsonBuilder.addSerializationExclusionStrategy(new ExclusionStrategy() { @Override public boolean shouldSkipField(FieldAttributes fieldAttributes) { String name=fieldAttributes.getName(); for(String filed: filedList){ if(filed.equals(name)){ return true; } } return false; } @Override public boolean shouldSkipClass(Class<?> clazz) { return false; } }); Gson gson=gsonBuilder.create(); String userInfoString=gson.toJson(userInfo); System.out.println(userInfoString); } }
然後我們再運行,得到結果如下:
{"id":1,"gender":false,"roleList":["admin","manager"],"createTime":"2018-10-25"}
2.2 SpringBoot中的GSON
因爲SpringBoot是支持SPI的,簡單理解就是能抓到哪個,就用哪個實現,因爲spring-boot-starter-web默認是用jackson,所以此時爲了能夠讓springboot抓到gson,我們一方面要在pom里加上gson的配置,另一方面還需要將jackson排除掉,如下所示:
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>top.lianmengtu</groupId> <artifactId>test-json</artifactId> <version>1.0-SNAPSHOT</version> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.6.RELEASE</version> </parent> <name>test-json</name> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>11</maven.compiler.source> <maven.compiler.target>11</maven.compiler.target> <lombok.version>1.18.2</lombok.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> <exclusions> <exclusion> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> </exclusion> <exclusion> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-annotations</artifactId> </exclusion> <exclusion> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-core</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>com.google.code.gson</groupId> <artifactId>gson</artifactId> <version>2.8.5</version> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>${lombok.version}</version> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>
這樣就可以在SpringBoot中啓用Gson了.我們可以打開日誌查看一下:
GsonAutoConfiguration matched: - @ConditionalOnClass found required class 'com.google.gson.Gson'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition) GsonAutoConfiguration#gson matched: - @ConditionalOnMissingBean (types: com.google.gson.Gson; SearchStrategy: all) did not find any beans (OnBeanCondition) GsonAutoConfiguration#gsonBuilder matched: - @ConditionalOnMissingBean (types: com.google.gson.GsonBuilder; SearchStrategy: all) did not find any beans (OnBeanCondition) GsonHttpMessageConvertersConfiguration matched: - @ConditionalOnClass found required class 'com.google.gson.Gson'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition) GsonHttpMessageConvertersConfiguration.GsonHttpMessageConverterConfiguration matched: - AnyNestedCondition 1 matched 1 did not; NestedCondition on GsonHttpMessageConvertersConfiguration.PreferGsonOrJacksonAndJsonbUnavailableCondition.JacksonJsonbUnavailable NoneNestedConditions 0 matched 2 did not; NestedCondition on GsonHttpMessageConvertersConfiguration.JacksonAndJsonbUnavailableCondition.JsonbPreferred @ConditionalOnProperty (spring.http.converters.preferred-json-mapper=jsonb) did not find property 'spring.http.converters.preferred-json-mapper'; NestedCondition on GsonHttpMessageConvertersConfiguration.JacksonAndJsonbUnavailableCondition.JacksonAvailable @ConditionalOnBean (types: org.springframework.http.converter.json.MappingJackson2HttpMessageConverter; SearchStrategy: all) did not find any beans of type org.springframework.http.converter.json.MappingJackson2HttpMessageConverter; NestedCondition on GsonHttpMessageConvertersConfiguration.PreferGsonOrJacksonAndJsonbUnavailableCondition.GsonPreferred @ConditionalOnProperty (spring.http.converters.preferred-json-mapper=gson) did not find property 'spring.http.converters.preferred-json-mapper' (GsonHttpMessageConvertersConfiguration.PreferGsonOrJacksonAndJsonbUnavailableCondition) - @ConditionalOnBean (types: com.google.gson.Gson; SearchStrategy: all) found bean 'gson' (OnBeanCondition)
現在我們來演示一下日期排除,Controller代碼如下:
package top.lianmengtu.testjson.controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import top.lianmengtu.testjson.domain.Company; import top.lianmengtu.testjson.domain.UserInfo; import java.util.ArrayList; import java.util.Date; import java.util.List; @RestController @RequestMapping("gson/") public class GsonController { @RequestMapping("basic") public UserInfo basic(){ UserInfo userInfo = new UserInfo(); userInfo.setId(1l); userInfo.setCreateTime(new Date()); userInfo.setNickName("Nick"); userInfo.setGender(false); List<String> roleList=new ArrayList<>(); roleList.add("admin"); roleList.add("manager"); userInfo.setRoleList(roleList); Company baidu=new Company(); baidu.setId(1l); baidu.setName("百度"); baidu.setAddress("西二旗"); List<Company> companies = new ArrayList<>(); companies.add(baidu); userInfo.setCompanies(companies); return userInfo; } }
與jackson配置類似,springboot支持gson,其相關配置在spring.gson下,yml配置修改如下:
spring: gson: date-format: 'yyyy-MM-dd HH:mm:ss'
運行後,結果如下:
{"id":1,"nickName":"Nick","gender":false,"roleList":["admin","manager"],"companies":[{"id":1,"name":"百度","address":"西二旗"}],"createTime":"2018-10-25 18:38:38"}
現在我們來演示字段排除,因爲transient是自動支持的,所以我們不再演示,我們來演示一下@Expose的使用,配置文件修改如下:
spring: gson: date-format: 'yyyy-MM-dd HH:mm:ss' exclude-fields-without-expose-annotation: true
然後實體類修改如下:
package top.lianmengtu.testjson.domain; import com.google.gson.annotations.Expose; import lombok.Getter; import lombok.Setter; import org.springframework.format.annotation.DateTimeFormat; import java.util.Date; import java.util.List; @Getter @Setter public class UserInfo { @Expose private Long id; @Expose private String nickName; private Boolean gender; private List<String> roleList; private List<Company> companies; private Date createTime; }
我們在id和nickName字段上加上@Expose,,然後運行代碼,效果如下所示:
{"id":1,"nickName":"Nick"}
除了這些之外,它支持的配置如下所示:
spring.gson.date-format= spring.gson.disable-html-escaping= spring.gson.disable-inner-class-serialization= spring.gson.enable-complex-map-key-serialization= spring.gson.exclude-fields-without-expose-annotation= spring.gson.field-naming-policy= spring.gson.generate-non-executable-json= spring.gson.lenient= spring.gson.long-serialization-policy= spring.gson.pretty-printing= spring.gson.serialize-nulls=
這裏有個屬性是disable-html-escaping,可以幫助我們過濾html標籤,這個在某些場景下還是很有用的
3. JSON-B
json-b是Java EE8中提供的一種json標準.該 API提供了適配器及一些自定義序列化器和反序列化器。對於較高級的場景,可以使用類中的註解或運行時配置構建器來覆蓋 JSON-B 的默認設置。
總而言之,JSON-B整理了已在企業開發人員中廣泛應用的行業實踐和方法。它使用註解通過映射語義來標記類和字段,提供了處理複雜數據結構時常常需要的可擴展性。
最重要的是,這個 API 支持以一種直觀且容易的方式在 Java 類與 JSON 文檔之間進行綁定。甚至沒有 JSON經驗的開發人員,應該也能夠輕鬆上手使用 Java API for JSON Binding。對 JSON 反/序列化庫(比如 GSON、Boon 和 Jackson)經驗豐富的開發人員將發現 JSON-B 很熟悉且用起來很舒適。
我們仍然從兩方面來闡述JSON-B的使用,首先是非SpringBoot項目中的使用,其次是SpringBoot項目中的使用
3.1 常規使用
json-b是一種規範,其中Yasson是eclipse實現的,而johnzon-jsonb則是apache實現的.因爲json-b是一種規範,所以我們只要加入實現即可,無論哪種實現,使用起來幾乎是一樣的,我們添加了Yasson,GAV座標如下:
<dependency> <groupId>org.eclipse</groupId> <artifactId>yasson</artifactId> <version>1.0.2</version> </dependency> <dependency> <groupId>org.glassfish</groupId> <artifactId>javax.json</artifactId> <version>1.1.2</version> </dependency>
測試代碼如下:
package top.lianmengtu.testjson; import top.lianmengtu.testjson.domain.Company; import top.lianmengtu.testjson.domain.UserInfo; import javax.json.bind.Jsonb; import javax.json.bind.JsonbBuilder; import java.util.ArrayList; import java.util.Date; import java.util.List; public class JSONBTest { public static void main(String[] args) { UserInfo userInfo = new UserInfo(); userInfo.setId(1l); userInfo.setCreateTime(new Date()); userInfo.setNickName("Nick"); userInfo.setGender(false); List<String> roleList=new ArrayList<>(); roleList.add("admin"); roleList.add("manager"); userInfo.setRoleList(roleList); Company baidu=new Company(); baidu.setId(1l); baidu.setName("百度"); baidu.setAddress("西二旗"); List<Company> companies = new ArrayList<>(); companies.add(baidu); userInfo.setCompanies(companies); Jsonb userJson=JsonbBuilder.create(); String userInfoString=userJson.toJson(userInfo); System.out.println(userInfoString); } }
運行代碼後的結果如下:
{"companies":[{"address":"西二旗","id":1,"name":"百度"}],"createTime":"2018-10-25T11:32:17.337Z[UTC]","gender":false,"id":1,"nickName":"Nick","roleList":["admin","manager"]}
首先,我們還是來看日期格式化的問題,測試代碼如下:
package top.lianmengtu.testjson; import top.lianmengtu.testjson.domain.Company; import top.lianmengtu.testjson.domain.UserInfo; import javax.json.bind.Jsonb; import javax.json.bind.JsonbBuilder; import javax.json.bind.JsonbConfig; import java.util.ArrayList; import java.util.Date; import java.util.List; import java.util.Locale; public class JSONBTest { public static void main(String[] args) { UserInfo userInfo = new UserInfo(); userInfo.setId(1l); userInfo.setCreateTime(new Date()); userInfo.setNickName("Nick"); userInfo.setGender(false); List<String> roleList=new ArrayList<>(); roleList.add("admin"); roleList.add("manager"); userInfo.setRoleList(roleList); Company baidu=new Company(); baidu.setId(1l); baidu.setName("百度"); baidu.setAddress("西二旗"); List<Company> companies = new ArrayList<>(); companies.add(baidu); userInfo.setCompanies(companies); JsonbConfig config=new JsonbConfig(); config.withDateFormat("yyyy-MM-dd",Locale.CHINESE); Jsonb userJson=JsonbBuilder.create(config); String userInfoString=userJson.toJson(userInfo); System.out.println(userInfoString); } }
運行就結果如下:
{"companies":[{"address":"西二旗","id":1,"name":"百度"}],"createTime":"2018-10-25","gender":false,"id":1,"nickName":"Nick","roleList":["admin","manager"]}
3.2 SpringBoot中的JSON-B
在springBoot中使用JSON-B的方式和GSON相似,我們只需要排除掉jackson然後添加上apache-johnzon的jackson就可以了.這裏我們添加的是Apache Johnzon. GAV座標如下:
<dependency> <groupId>org.apache.johnzon</groupId> <artifactId>johnzon-jsonb</artifactId> <version>1.1.10</version> </dependency> <dependency> <groupId>org.apache.johnzon</groupId> <artifactId>jsonb-api</artifactId> <version>1.0.0</version> </dependency>
配置文件如下所示:
JsonbHttpMessageConvertersConfiguration matched: - @ConditionalOnClass found required class 'javax.json.bind.Jsonb'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition)
我們看懂這裏匹配到的是jsonb,這說明我們的配置已經成功了.controller不變,我們打開瀏覽器,然後訪問localhost:8080/jsonb/basic,結果如下所示:
{"companies":[{"address":"西二旗","id":1,"name":"百度"}],"createTime":"2018-10-25","gender":false,"id":1,"nickName":"Nick","roleList":["admin","manager"]}