体验Jackson Json

体验了一把Jackson Json。

将对象（List, Map, POJO Object）转换为json字符串: 

可使用方法 ObjectMapper#writeValueAsString(Object value)

例：

list2Json();

map2Json();

pojo2Json();

将Json字符串转换为对象（List, Map, POJO Object）: 

可使用方法 ObjectMapper#readValue(String content, Class<T> valueType)

例：

json2List();

json2Map();

json2Pojo();

测试程序如下：

import java.io.IOException;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import org.codehaus.jackson.JsonGenerationException;import org.codehaus.jackson.JsonParseException;import org.codehaus.jackson.map.JsonMappingException;import org.codehaus.jackson.map.ObjectMapper;public class ConvertTest {public static void main(String[] args) {new ConvertTest().todo();}private ObjectMapper mapper = new ObjectMapper();public void todo() {System.out.println("============ Object To JSON ============");list2Json();map2Json();pojo2Json();System.out.println("============ JSON TO Object ============");json2List();json2Map();json2Pojo();}public void list2Json() {List list = new ArrayList();Map m1 = new HashMap();m1.put("first", "Joe");m1.put("last", "Sixpack");m1.put("gender", "MALE");m1.put("verified", false);list.add(m1);Map m2 = new HashMap();m2.put("first", "Joe");m2.put("last", "Sixpack");m2.put("address", "unknown");list.add(m2);String output;try {output = mapper.writeValueAsString(list);System.out.println(output);// print '[{"last":"Sixpack","verified":false,"gender":"MALE","first":"Joe"},{"last":"Sixpack","address":"unknown","first":"Joe"}]'} catch (JsonGenerationException e) {e.printStackTrace();} catch (JsonMappingException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}public void map2Json() {Map m = new HashMap();Map m1 = new HashMap();m1.put("first", "Joe");m1.put("last", "Sixpack");m.put("name", m1);m.put("gender", "MALE");m.put("verified", false);String output;try {output = mapper.writeValueAsString(m);System.out.println(output); // print '{"verified":false,"name":{"last":"Sixpack","first":"Joe"},"gender":"MALE"}'} catch (JsonGenerationException e) {e.printStackTrace();} catch (JsonMappingException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}public void pojo2Json() {User user = new User();User.Name name = new User.Name();name.setFirst("Joe");name.setLast("Sixpack");user.setName(name);user.setVerified(false);String output;try {output = mapper.writeValueAsString(user);System.out.println(output); // print '{"verified":false,"name":{"first":"Joe","last":"Sixpack"}}'} catch (JsonGenerationException e) {e.printStackTrace();} catch (JsonMappingException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}public void json2List() {String json = "[" +"{" + "\"name\" : { \"first\" : \"Joe\", \"last\" : \"Sixpack\" }, " +  "\"gender\" : \"MALE\", " +"\"verified\" : false" + "}" + ", " + "{" + "\"name\" : { \"first\" : \"Joe\", \"last\" : \"Sixpack\" }, " +  "\"address\" : \"unknown\" " + "}" + "]";try {List li = mapper.readValue(json, List.class);System.out.println(li); // print '[{name={first=Joe, last=Sixpack}, gender=MALE, verified=false}, {name={first=Joe, last=Sixpack}, address=unknown}]'String address = (String)((Map)li.get(1)).get("address");System.out.println("list(0) => address : " + address); // print 'list(0) => address : unknown'} catch (JsonParseException e) {e.printStackTrace();} catch (JsonMappingException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}public void json2Map() {String json = "{" + "\"name\" : { \"first\" : \"Joe\", \"last\" : \"Sixpack\" }, " +  "\"gender\" : \"MALE\", " +"\"verified\" : false" + "}";try {Map m = mapper.readValue(json, Map.class);Object o = ((Map)m.get("name")).get("first");System.out.println((String)o); // print 'Joe'System.out.println(m); // print '{name={first=Joe, last=Sixpack}, gender=MALE, verified=false}'} catch (JsonParseException e) {e.printStackTrace();} catch (JsonMappingException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}public void json2Pojo() {String json = "{" + "\"name\" : { \"first\" : \"Joe\", \"last\" : \"Sixpack\" }, " +  "\"verified\" : false" + "}";try {User u = mapper.readValue(json, User.class);// print // name=>Joe Sixpack// verified=>falseSystem.out.println(u);} catch (JsonParseException e) {e.printStackTrace();} catch (JsonMappingException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}public static class User {public static class Name {  private String _first, _last;  public String getFirst() { return _first; }  public String getLast() { return _last; }  public void setFirst(String s) { _first = s; }  public void setLast(String s) { _last = s; }  public String toString() {  return "name=>" + _first + " " + _last;  }}private Name _name;private boolean _isVerified;public Name getName() { return _name; }public boolean isVerified() { return _isVerified; }public void setName(Name n) { _name = n; }public void setVerified(boolean b) { _isVerified = b; }public String toString() {return _name.toString() + "\nverified=>" + _isVerified;}}}

Ref: http://jackson.codehaus.org/