Java Object and JSON data mapping by FasterXML Jackson

1. SoftLeader Tech. Corp.
2014.07
Jackson Training

2. Main Projects
• jackson-core
• jackson-annotations
• jackson-databind
• Third-party
 Guava
 Hibernate
 HPPC
 Joda
 org.json
 JSR-310 ( Java 8 Date )
 JSR-353 ( Java JSON API )
 JDK7

3. Maven
• groupId : com.fasterxml.jackson.core
• artifactId:
 jackson-core
 jackson-databind
 jackson-annotations
• version
 now is 2.4.0

4. What is JSON format
{
"id": 1,
"account": "admin",
"name": "Administrator"
}
if in XML , too complex and bigger size.
<root>
<user id= "1">
<account>admin</account>
<name>Administrator</name>
</user>
</root>

5. JSON is simpler
• Property
{"attribute1 ": "string ", "attribute2 ": number}
• List
{"attribute3 ": ["Apple", "Banana", "Cherry"]}
• Map/Object
{"attribute4":{"field1":"value1", "field2":"value2"}}

6. JSON Parser
• Streaming
• Tree Traversing
• Data Binding

7. Data Binding
ObjectMapper objectMapper = new ObjectMapper();
mapper.readValue( src, MyBean.class);
MyBean myBean = new MyBean();
mapper.writeValue(dst, myBean);
• File
• InputStream / OutputStream
• Reader / Writer
• String

8. Java Mapping
JSON Type Java Type
object LinkedHashMap<String, Object>
array ArrayList<Object>
string String
number ( no fraction) Integer, Long, BigInteger
number ( fraction ) Double (  BigDecimal )
true/false Boolean
null null

9. Basic Annotations
• @JsonProperty 對應到 json 的屬性值
• @JsonIgnore 忽略輸入與輸出 // property level
• @JsonIgnoreProperties({.., ..}) // class level
• @JsonIgnoreProperties(ignoreUnknown=true)

10. parent-child
• @JsonTypeInfo(use=Id.CLASS, include=As.PROPERTY,
property="softleader@class")
{
"pets":[
{
"name":"Mars",
"softleader@class":"tw.com.softleader.json.jackson.entity.Question07Dog",
"age":7
},
{
"name":"Tiger",
"softleader@class":"tw.com.softleader.json.jackson.entity.Question07Cat",
"color":"yellow“
}
]
}

11. Joda-time
• jackson-datatype-joda
ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new JodaModule());

12. Q & A