Jackson 使用和注意项
依赖maven:
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.6.5</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.6.5</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
<version>2.6.5</version>
</dependency>
code:
User:
import lombok.*; @Data @ToString @NoArgsConstructor @AllArgsConstructor public class User { private int id; private String name; private String email; private String address; private Birthday birthday; }
Birthday:
import lombok.*; @Data @ToString @NoArgsConstructor @AllArgsConstructor public class Birthday { private String birthday; }
User2:
import lombok.AllArgsConstructor; import lombok.Data; import lombok.NoArgsConstructor; import lombok.ToString; @Data @ToString @NoArgsConstructor @AllArgsConstructor public class User2 { private int id; private String name; private String email; // private String address; // private Birthday birthday; }
1.查看基础类型的序列化与反序列化：
import com.fasterxml.jackson.databind.ObjectMapper; import lombok.val; import java.io.IOException; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; public class test{ private final static ObjectMapper objectMapper = new ObjectMapper(); public static void main(String[] args) { User user = new User(); user.setAddress("asdf"); user.setAddress("中国河南省"); user.setEmail("xiaokui_wingfly@sina.com.cn"); user.setId(1); user.setName("X-rapido"); user.setBirthday(new Birthday("2015-08-06")); List<String> list = new ArrayList<String>(); list.add("a"); list.add("b"); list.add("c"); Map<String, Object> map = new HashMap<String, Object>(); map.put("a", "1"); map.put("b", "2"); map.put("c", "3"); map.put("list", list); String []sz = {"a","b","c"}; try { System.out.println(objectMapper.writeValueAsString(user)); System.out.println(objectMapper.writeValueAsString(list)); System.out.println(objectMapper.writeValueAsString(map)); System.out.println(objectMapper.writeValueAsString(sz)); String s = "{\"name\":\"X-rapido\"}"; // Json转换JavaBean User a = objectMapper.readValue(s, User.class); System.out.println(a.getName()); // JavaBean转换Json System.out.println(objectMapper.writeValueAsString(a)); } catch (IOException e) { e.printStackTrace(); } } }
Output:
{"id":1,"name":"X-rapido","email":"xiaokui_wingfly@sina.com.cn","address":"中国河南省","birthday":{"birthday":"2015-08-06"}}
["a","b","c"]
{"a":"1","b":"2","c":"3","list":["a","b","c"]}
["a","b","c"]
X-rapido
{"id":0,"name":"X-rapido","email":null,"address":null,"birthday":null}
2.有这么种情况，就是字符串反序列化为对象，但是字符串中的很多字段我都不需要，只需要一部分，这个时候怎么反序列化：
import com.fasterxml.jackson.databind.DeserializationFeature; import com.fasterxml.jackson.databind.ObjectMapper; import lombok.val; import java.io.IOException; public class test{ private final static ObjectMapper objectMapper = new ObjectMapper(); public static void main(String[] args) { //当反序列化json时，未知属性会引起的反序列化被打断，这里我们禁用未知属性打断反序列化功能， //因为，例如json里有10个属性，而我们的bean中只定义了2个属性，其它8个属性将被忽略 objectMapper .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES); User user = new User(); user.setAddress("asdf"); user.setAddress("中国河南省"); user.setEmail("xiaokui_wingfly@sina.com.cn"); user.setId(1); user.setName("X-rapido"); user.setBirthday(new Birthday("2015-08-06")); try { System.out.println("========begin======="); val content=objectMapper.writeValueAsString(user); System.out.println(content); User2 u=objectMapper.readValue(content,User2.class); System.out.println(objectMapper.writeValueAsString(u)); System.out.println("========end======="); } catch (IOException e) { e.printStackTrace(); } } }
Output:
========begin======= {"id":1,"name":"X-rapido","email":"xiaokui_wingfly@sina.com.cn","address":"中国河南省","birthday":{"birthday":"2015-08-06"}} {"id":1,"name":"X-rapido","email":"xiaokui_wingfly@sina.com.cn"} ========end=======
注意：
objectMapper .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
如果不加这个会报错：
========begin======= {"id":1,"name":"X-rapido","email":"xiaokui_wingfly@sina.com.cn","address":"中国河南省","birthday":{"birthday":"2015-08-06"}} com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "address" (class com.qhong.json.User2), not marked as ignorable (3 known properties: "id", "email", "name"]) at [Source: {"id":1,"name":"X-rapido","email":"xiaokui_wingfly@sina.com.cn","address":"中国河南省","birthday":{"birthday":"2015-08-06"}}; line: 1, column: 76] (through reference chain: com.qhong.json.User2["address"]) at com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException.from(UnrecognizedPropertyException.java:51) at com.fasterxml.jackson.databind.DeserializationContext.reportUnknownProperty(DeserializationContext.java:839) at com.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty(StdDeserializer.java:1045) at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownProperty(BeanDeserializerBase.java:1352) at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownVanilla(BeanDeserializerBase.java:1330) at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:264) at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:125) at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3736) at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2726) at com.qhong.json.test.main(test.java:29)
3.怎么反序列化对象数组：
import com.fasterxml.jackson.databind.DeserializationFeature; import com.fasterxml.jackson.databind.ObjectMapper; import lombok.val; import java.io.IOException; import java.util.ArrayList; import java.util.Arrays; import java.util.List; public class test{ private final static ObjectMapper objectMapper = new ObjectMapper(); public static void main(String[] args) { //当反序列化json时，未知属性会引起的反序列化被打断，这里我们禁用未知属性打断反序列化功能， //因为，例如json里有10个属性，而我们的bean中只定义了2个属性，其它8个属性将被忽略 objectMapper .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES); List<User> arr= Arrays.asList( new User(1, "name1", "email1", "address1", new Birthday("2016-08-01")), new User(2 ,"name2", "email2", "address2", new Birthday("2016-08-02")), new User(3, "name3", "email3", "address3", new Birthday("2016-08-03")) ); try { System.out.println("========begin======="); val content=objectMapper.writeValueAsString(arr); System.out.println(content); List<User> list=objectMapper.readValue(content,new com.fasterxml.jackson.core.type.TypeReference<List<User>>(){}); System.out.println(objectMapper.writeValueAsString(list)); System.out.println("另外的方式："); // List<MyClass> myObjects = mapper.readValue(jsonInput, mapper.getTypeFactory().constructCollectionType(List.class, MyClass.class)); List<User> list2=objectMapper.readValue(content,objectMapper.getTypeFactory().constructCollectionType(ArrayList.class,User.class)); System.out.println(objectMapper.writeValueAsString(list2)); System.out.println("========end======="); } catch (IOException e) { e.printStackTrace(); } } }
Output:
========begin======= [{"id":1,"name":"name1","email":"email1","address":"address1","birthday":{"birthday":"2016-08-01"}},{"id":2,"name":"name2","email":"email2","address":"address2","birthday":{"birthday":"2016-08-02"}},{"id":3,"name":"name3","email":"email3","address":"address3","birthday":{"birthday":"2016-08-03"}}] [{"id":1,"name":"name1","email":"email1","address":"address1","birthday":{"birthday":"2016-08-01"}},{"id":2,"name":"name2","email":"email2","address":"address2","birthday":{"birthday":"2016-08-02"}},{"id":3,"name":"name3","email":"email3","address":"address3","birthday":{"birthday":"2016-08-03"}}] 另外的方式： [{"id":1,"name":"name1","email":"email1","address":"address1","birthday":{"birthday":"2016-08-01"}},{"id":2,"name":"name2","email":"email2","address":"address2","birthday":{"birthday":"2016-08-02"}},{"id":3,"name":"name3","email":"email3","address":"address3","birthday":{"birthday":"2016-08-03"}}] ========end=======
还有一些其他的特殊情况，比如json对象key没有双引号等
import com.fasterxml.jackson.annotation.JsonInclude; import com.fasterxml.jackson.core.JsonGenerator; import com.fasterxml.jackson.core.JsonParser; import com.fasterxml.jackson.core.type.TypeReference; import com.fasterxml.jackson.databind.DeserializationFeature; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.SerializationFeature; import lombok.AllArgsConstructor; import lombok.Data; import lombok.NoArgsConstructor; import lombok.ToString; import java.util.List; public class test2{ private final static ObjectMapper mapper= new ObjectMapper(); public static void main(String[] args) { try { mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES); // 如果为空则不输出 mapper.setSerializationInclusion(JsonInclude.Include.NON_EMPTY); // 对于空的对象转json的时候不抛出错误 mapper.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS); // 禁用序列化日期为timestamps mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS); // 禁用遇到未知属性抛出异常 mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES); // 视空字符传为null mapper.enable(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT); // 低层级配置 mapper.configure(JsonParser.Feature.ALLOW_COMMENTS, true); // 允许属性名称没有引号 mapper.configure(JsonParser.Feature.ALLOW_UNQUOTED_FIELD_NAMES, true); // 允许单引号 mapper.configure(JsonParser.Feature.ALLOW_SINGLE_QUOTES, true); // 取消对非ASCII字符的转码 mapper.configure(JsonGenerator.Feature.ESCAPE_NON_ASCII, false); //mapper.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS); String str = " [\n" + " {\n" + " \"symbol\": \"sh603111\", \n" + " \"code\": \"603111\", \n" + " \"name\": \"康尼机电\", \n" + " \"trade\": \"14.530\", \n" + " \"pricechange\": \"0.770\", \n" + " \"changepercent\": \"5.596\", \n" + " \"buy\": \"14.530\", \n" + " \"sell\": \"14.540\", \n" + " \"settlement\": \"13.760\", \n" + " \"open\": \"13.820\", \n" + " \"high\": \"14.540\", \n" + " \"low\": \"13.820\", \n" + " \"volume\": 18591408, \n" + " \"amount\": 266138177, \n" + " \"ticktime\": \"15:00:00\", \n" + " \"per\": 44.339, \n" + " \"pb\": 7.731, \n" + " \"mktcap\": 1072870.86225, \n" + " \"nmc\": 697004.688465, \n" + " \"turnoverratio\": 3.87563\n" + " }, \n" + " {\n" + " \"symbol\": \"sz300355\", \n" + " \"code\": \"300355\", \n" + " \"name\": \"蒙草生态\", \n" + " \"trade\": \"12.330\", \n" + " \"pricechange\": \"0.620\", \n" + " \"changepercent\": \"5.295\", \n" + " \"buy\": \"12.330\", \n" + " \"sell\": \"12.340\", \n" + " \"settlement\": \"11.710\", \n" + " \"open\": \"11.640\", \n" + " \"high\": \"12.580\", \n" + " \"low\": \"11.640\", \n" + " \"volume\": 142839605, \n" + " \"amount\": 1741652819, \n" + " \"ticktime\": \"15:06:03\", \n" + " \"per\": 35.229, \n" + " \"pb\": 6.27, \n" + " \"mktcap\": 1978030.485873, \n" + " \"nmc\": 1428385.32288, \n" + " \"turnoverratio\": 12.33009\n" + " }\n" + "]"; System.out.println(str); List<riseInfo> list = mapper.readValue(str, new TypeReference<List<riseInfo>>() { }); System.out.println(list.size()); }catch (Exception ex){ System.out.println(ex.getMessage()); System.out.println(ex.getStackTrace()); } } } @Data @ToString @NoArgsConstructor @AllArgsConstructor class riseInfo { private String symbol; private String code; private String name; }
Output:
[ { "symbol": "sh603111", "code": "603111", "name": "康尼机电", "trade": "14.530", "pricechange": "0.770", "changepercent": "5.596", "buy": "14.530", "sell": "14.540", "settlement": "13.760", "open": "13.820", "high": "14.540", "low": "13.820", "volume": 18591408, "amount": 266138177, "ticktime": "15:00:00", "per": 44.339, "pb": 7.731, "mktcap": 1072870.86225, "nmc": 697004.688465, "turnoverratio": 3.87563 }, { "symbol": "sz300355", "code": "300355", "name": "蒙草生态", "trade": "12.330", "pricechange": "0.620", "changepercent": "5.295", "buy": "12.330", "sell": "12.340", "settlement": "11.710", "open": "11.640", "high": "12.580", "low": "11.640", "volume": 142839605, "amount": 1741652819, "ticktime": "15:06:03", "per": 35.229, "pb": 6.27, "mktcap": 1978030.485873, "nmc": 1428385.32288, "turnoverratio": 12.33009 } ] 2
添加配置即可！
http://blog.csdn.net/langzi7758521/article/details/52072457
http://www.cnblogs.com/kakag/p/5054772.html
