jackson簡單使用，對象轉json，json轉對象，json轉list
POJO序列化為json字符串：
准備一個POJO：
@JsonIgnoreProperties(ignoreUnknown = true) class User implements Serializable { private static final long serialVersionUID = -5952920972581467417L; private String name; public User() { } public User(String name) { this.name = name; } public String getName() { return name; } @Override public String toString() { return "User{" + "name=" + name + '}'; } }
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@JsonIgnoreProperties(ignoreUnknown = true) 是為了反序列化的時候，如果遇到不認識的filed，忽略之
- 無參構造函數是為了在反序列化的時候，jackson可以創建POJO實例
- getter方法是為了序列化的時候，jackson可以獲取filed值
- toString是方便我自己debug看顯示
- 至於Serializable，習慣的給實體增加一個持久化的能力。
通過write來轉化成jason字符串：
String expected = "{\"name\":\"Test\"}";
String test = mapper.writeValueAsString(new User("Test")); Assert.assertEquals(expected, test);
通過read來parse json字符串為POJO對象：
User user = mapper.readValue(expected, User.class); Assert.assertEquals("Test", user.getName());
jsonArray轉換成Array數組：
String expected = "[{\"name\":\"Ryan\"},{\"name\":\"Test\"},{\"name\":\"Leslie\"}]";
ArrayType arrayType = mapper.getTypeFactory().constructArrayType(User.class); User[] users = mapper.readValue(expected, arrayType); Assert.assertEquals("Ryan", users[0].getName());
jsonArray轉換成List<>泛型：
expected="[{\"a\":12},{\"b\":23},{\"name\":\"Ryan\"}]";
CollectionType listType = mapper.getTypeFactory().constructCollectionType(ArrayList.class, User.class); //the sieze of the list is dependon the str json length although the json content is not the POJO type maybe List<User> userList = mapper.readValue(expected, listType); Assert.assertEquals(3, userList.size()); Assert.assertNull(userList.get(0).getName()); Assert.assertEquals("Ryan",userList.get(2).getName());
jackson默認將對象轉換為LinkedHashMap：
String expected = "[{\"name\":\"Ryan\"},{\"name\":\"Test\"},{\"name\":\"Leslie\"}]";
ArrayList arrayList = mapper.readValue(expected, ArrayList.class); Object o = arrayList.get(0); Assert.assertTrue(o instanceof LinkedHashMap);
轉載：http://www.cnblogs.com/woshimrf/p/5847262.html