ObjectMapper类是Jackson库的主要类。它提供一些功能将转换成Java对象匹配JSON结构，反之亦然。它使用JsonParser和JsonGenerator的实例实现JSON实际的读/写。
类声明
以下是org.codehaus.jackson.map.ObjectMapper类的声明：
|
1
2
3
|
public class ObjectMapper extends ObjectCodec implements Versioned |
嵌套类
|
S.N. |
类 & 描述 |
|---|---|
|
1 |
static class ObjectMapper.DefaultTypeResolverBuilder//定制TypeResolverBuilder，提供所谓的“默认输入”使用类型解析构建器（见enableDefaultTyping()了解详细信息）。 |
|
2 |
static class ObjectMapper.DefaultTyping//使用enableDefaultTyping()枚举指定什么样的类型（类）默认输入应该使用。 |
构造函数
|
S.N. |
构造函数 & 描述 |
|---|---|
|
1 |
ObjectMapper()//默认的构造函数，这将构建默认JsonFactory必要时使用StdSerializerProvider作为其SerializerProvider，并BeanSerializerFactory作为其SerializerFactory。 |
|
2 |
ObjectMapper(JsonFactory jf)//构造使用指定的JsonFactory构建必要的JsonParsers和/或JsonGenerators映射。 |
|
3 |
ObjectMapper(JsonFactory jf, SerializerProvider sp, DeserializerProvider dp) |
|
4 |
ObjectMapper(JsonFactory jf, SerializerProvider sp, DeserializerProvider dp, SerializationConfig sconfig, DeserializationConfig dconfig) |
|
5 |
ObjectMapper(SerializerFactory sf) 不推荐使用。使用其他构造来代替; 注意，可以设置序列化工厂setSerializerFactory（org.codehaus.jackson.map.SerializerFactory） |
这个类继承了以下类方法：
java.lang.Object
例子
测试类基本代码如下
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
|
/* * @project java * @package * @file Jackson.java * @version 1.0 */ public class Jackson { /* * * Class Descripton goes here. * * @class Jackson * @version 1.0 */ public static JsonGenerator jsonGenerator = null; private static ObjectMapper mapper = new ObjectMapper(); public static void main(String[] args) { Student student = new Student(); student.setIsstudent(true); student.setUid(1000); student.setUname("xiao liao"); student.setUpwd("123"); student.setNumber(12); Map<String, Student> stuMap = new HashMap<String, Student>(); stuMap.put("1", student); stuMap.put("2", student); List<Object> stuList = new ArrayList<Object>(); List<Student> stuList1 = new ArrayList<Student>(); stuList1.add(student); student= new Student(); student.setIsstudent(false); student.setUid(200); student.setUname("xiao mi"); stuList1.add(student); stuList.add(student); stuList.add("xiao xin"); stuList.add("xiao er"); stuList.add(stuMap); //readJson2List(); try { //readJson2Array(); //writeArray2Json(array); //writeJson2List(); //writeEntity2Json(student); writeJson2Entity(); //writeMap2Json(stuMap); //writeList2Json(stuList1); } catch (IOException e) { e.printStackTrace(); } } /** * * <code>writeEntity2Json</code> * @description: TODO(实体类转换成json) * @param object * @throws IOException */ public static void writeEntity2Json(Object object) throws IOException { mapper.writeValue( new File("D:\\developSoft\\aaadowload\\testjson1\\lib\\aa.txt"),object ); mapper.writeValue( System.out,object ); } /** * * <code>writeArray2Json</code> * @description: TODO(数组转换成json数组) * @param object * @throws IOException */ public static void writeArray2Json(Object object) throws IOException { // writeValue具有和writeObject相同的功能 mapper.writeValue( new File("D:\\developSoft\\aaadowload\\testjson1\\lib\\aa.txt"),object ); mapper.writeValue(System.out,object ); } /** * * <code>writeMap2Json</code> * @description: TODO(map对象转换成json对象) * @param object * @throws IOException * @since 2011-11-8 廖益平 */ public static void writeMap2Json(Object object) throws IOException { System.out.println("使用ObjectMapper-----------"); // writeValue具有和writeObject相同的功能 System.out.println("==>"+mapper.writeValueAsString(object)); mapper.writeValue( new File("D:\\developSoft\\aaadowload\\testjson1\\lib\\aamap.txt"),object ); mapper.writeValue( System.out , object ); } /** * * <code>writeList2Json</code> * @description: TODO(list转换成json) * @param object * @throws IOException */ public static void writeList2Json(Object object) throws IOException { System.out.println("==>"+mapper.writeValueAsString(object)); mapper.writeValue( new File("D:\\developSoft\\aaadowload\\testjson1\\lib\\aamap.txt"),object ); mapper.writeValue( System.out , object ); } /** * * <code>writeJson2Entity</code> * @description: TODO(json转换成实体) * @throws IOException */ public static void writeJson2Entity() throws IOException { System.out.println("json串转换成entity-------------"); // File file = new File("D:\\developSoft\\aaadowload\\testjson1\\lib\\aa.txt"); // FileInputStream inputStream = new FileInputStream(file); // Student student = mapper.readValue(inputStream,Student.class); // System.out.println(student.toString()); //漂亮输出 //mapper.defaultPrettyPrintingWriter().writeValueAsString(value); String json = "{\"uid\":1000,\"uname\":\"xiao liao\",\"upwd\":\"123\",\"number\":12.0,\"isstudent\":true}"; Student student1 = mapper.readValue(json,Student.class); System.out.println("json2:"+student1.toString()); } /** * * <code>writeJson2List</code> * @description: TODO(json专程list对象) * @throws IOException */ public static void writeJson2List() throws IOException { System.out.println("json串转换成entity-------------"); File file = new File("D:\\developSoft\\aaadowload\\testjson1\\lib\\aa.txt"); FileInputStream inputStream = new FileInputStream(file); Student student = mapper.readValue(inputStream,Student.class); System.out.println(student.toString()); String json = "[{\"uid\":1000,\"uname\":\"xiao liao\",\"upwd\":\"123\",\"number\":12.0,\"isstudent\":true},{\"uid\":200,\"uname\":\"xiao mi\",\"upwd\":null,\"number\":0.0,\"isstudent\":false}]"; List<LinkedHashMap<String, Object>> s= mapper.readValue(json,List.class); for (int i = 0; i < s.size(); i++) { LinkedHashMap<String, Object> link = s.get(i); Set<String> key = link.keySet(); for (Iterator iterator = key.iterator(); iterator.hasNext();) { String string = (String) iterator.next(); System.out.println(string+"==>"+link.get(string)); } System.out.println("json:"+i+""+s.get(i).toString()); } } /** * JSON转换为List对象 */ public static void readJson2List() { String json = "[{\"uid\":1,\"uname\":\"www\",\"number\":234,\"upwd\":\"456\"}," + "{\"uid\":5,\"uname\":\"tom\",\"number\":3.44,\"upwd\":\"123\"}]"; try { List<LinkedHashMap<String, Object>> list = mapper.readValue( json, List.class); System.out.println(list.size()); for (int i = 0; i < list.size(); i++) { Map<String, Object> map = list.get(i); Set<String> set = map.keySet(); for (Iterator<String> it = set.iterator(); it.hasNext();) { String key = it.next(); System.out.println(key + ":" + map.get(key)); } } } catch (JsonParseException e) { e.printStackTrace(); } catch (JsonMappingException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } /** * JSON转换为List对象 */ public static void readJson2Array() { String json = "[{\"uid\":1,\"uname\":\"www\",\"number\":234,\"upwd\":\"456\"}," + "{\"uid\":5,\"uname\":\"tom\",\"number\":3.44,\"upwd\":\"123\"}]"; try { Student[] students = mapper.readValue(json, Student[].class); for (Student student : students) { System.out.println(">"+student.toString()); } } catch (JsonParseException e) { e.printStackTrace(); } catch (JsonMappingException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } } |
打印结果 ：
|
1
2
3
4
5
6
7
8
9
10
11
|
串转换成entity-------------json2:uid=1000,name=xiao liao,upwd=123,number=12.0,isStudent=truewriteMap2Json -----------{"2":{"uid":1000,"uname":"xiao liao","upwd":"123","number":12.0,"isstudent":true},"1":{"uid":1000,"uname":"xiao liao","upwd":"123","number":12.0,"isstudent":true}}readJson2Array------------------>uid=1,name=www,upwd=456,number=234.0,isStudent=false>uid=5,name=tom,upwd=123,number=3.44,isStudent=falsewriteMap2Json -----------{"2":{"uid":1000,"uname":"xiao liao","upwd":"123","number":12.0,"isstudent":true},"1":{"uid":1000,"uname":"xiao liao","upwd":"123","number":12.0,"isstudent":true}} |
大家逐个自己试试吧 ，上面也是我的测试代码
