Jackson可以轻松的将Java对象转换成为json对象和xml对象,同样也可以将json,xml转换成Java对象。不仅限于对Java对象,对于Map,List,Array同样有效。
将对象转化成字节数组
public byte[] writeValueAsBytes(Object value)
将字节数组转换成简单对象
public <T> T readValue(byte[] src, Class<T> valueType)
将对象转化成json
public String writeValueAsString(Object value)
将json字符串转换成对象
public <T> T readValue(String content, Class<T> valueType)
maven中添加Jackson的相关依赖:
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>${jackson.version}</version>
</dependency>
简单的Json和JavaBean,简单的数据类型之间的转换
//JavaBean/Map/List/Array
public static void main(String[] args) {
ObjectMapper objectMapper = new ObjectMapper();
User user = new User();
user.setId(1);
user.setName("whw");
List<String> list = new ArrayList<>();
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);
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));
User a = objectMapper.readValue(s, User.class);
System.out.println(a.getName());
} catch (IOException e) {
e.printStackTrace();
}
}
输出打印:
{"id":1,"name":"whw"}
["a","b","c"]
{"b":"2","c":"3","a":"1","list":["a","b","c"]}
["a","b","c"]
whw
字节数组转换成复杂的列表对象
对于简单的对象来说可以直接使用其类的限定名,如java.lang.String等
对于复杂的列表对象来说,例如:java.utils.Map<java.lang.String, java.util.List>,这类需要使用:getTypeFactory().constructFromCanonical(type)
转化成JavaType再进行类型转化;
/**
* 将字节数组转换成对象
* 对于简单对象来说type就是其类的全限定名,如java.lang.String;
* 对于复杂列表对象来说,type例子:java.util.Map<java.lang.String, java.util.List<test.Person>>
*/
public static Object byteToObject(byte[] bytes, String type) {
JavaType javaType = MAPPER.getTypeFactory().constructFromCanonical(type);
try {
Object object = MAPPER.readValue(bytes, javaType);
return object;
} catch (IOException e) {
e.printStackTrace();
LOGGER.error("bytesToObject error");
}
return null;
}