在解析JSON方面，无疑JACKSON是做的最好的，下面从几个方面简单复习下。
1 JAVA 对象转为JSON
1.
2. import
3. import
4. import
5. import
6. import
7.
8. public class
9. public static void
10.
11. new
12. new
13.
14. try
15.
16. // convert user object to json string, and save to a file
17. new File("c:\\user.json"), user);
18.
19. // display to console
20. System.out.println(mapper.writeValueAsString(user));
21.
22. catch
23.
24. e.printStackTrace();
25.
26. catch
27.
28. e.printStackTrace();
29.
30. catch
31.
32. e.printStackTrace();
33.
34. }
35.
36. }
37.
import java.io.File;
import java.io.IOException;
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
public class JacksonExample {
public static void main(String[] args) {
User user = new User();
ObjectMapper mapper = new ObjectMapper();
try {
// convert user object to json string, and save to a file
mapper.writeValue(new File("c:\\user.json"), user);
// display to console
System.out.println(mapper.writeValueAsString(user));
} catch (JsonGenerationException e) {
e.printStackTrace();
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
输出为：
{"age":29,"messages":["msg 1","msg 2","msg 3"],"name":"mkyong"}
2 JSON反序列化为JAVA对象
1. import
2. import
3. import
4. import
5. import
6.
7. public class
8. public static void
9.
10. new
11.
12. try
13.
14. // read from file, convert it to user class
15. new File("c:\\user.json"), User.class);
16.
17. // display to console
18. System.out.println(user);
19.
20. catch
21.
22. e.printStackTrace();
23.
24. catch
25.
26. e.printStackTrace();
27.
28. catch
29.
30. e.printStackTrace();
31.
32. }
33.
34. }
35.
import java.io.File;
import java.io.IOException;
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
public class JacksonExample {
public static void main(String[] args) {
ObjectMapper mapper = new ObjectMapper();
try {
// read from file, convert it to user class
User user = mapper.readValue(new File("c:\\user.json"), User.class);
// display to console
System.out.println(user);
} catch (JsonGenerationException e) {
e.printStackTrace();
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
import java.io.File;
import java.io.IOException;
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
public class JacksonExample {
public static void main(String[] args) {
ObjectMapper mapper = new ObjectMapper();
try {
// read from file, convert it to user class
User user = mapper.readValue(new File("c:\\user.json"), User.class);
// display to console
System.out.println(user);
} catch (JsonGenerationException e) {
e.printStackTrace();
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
输出：User [age=29, name=mkyong, messages=[msg 1, msg 2, msg 3]]
3 在上面的例子中，如果要输出的JSON好看点，还是有办法的，就是使用
defaultPrettyPrintingWriter()方法，例子为：
1. User user = new
2. new
3. System.out.println(mapper.defaultPrettyPrintingWriter().writeValueAsString(user));
User user = new User();
ObjectMapper mapper = new ObjectMapper();
System.out.println(mapper.defaultPrettyPrintingWriter().writeValueAsString(user));
则输出整齐：
{
"age" : 29,
"messages" : [ "msg 1", "msg 2", "msg 3" ],
"name" : "mkyong"
}
