ObjectMapper使用
在项目中使用到了ObjectMapper,故研究了一下。现将自己的几个测试用例和大家分享一下~
首先在pom.xml文件中,加入依赖:
<dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.8.3</version> </dependency>
创建一个实体类XwjUser:
public class XwjUser implements Serializable { private static final long serialVersionUID = 1L; private int id; private String message; private Date sendTime; // 这里手写字母大写,只是为了测试使用,是不符合java规范的 private String NodeName; private List<Integer> intList; public XwjUser() { super(); } public XwjUser(int id, String message, Date sendTime) { super(); this.id = id; this.message = message; this.sendTime = sendTime; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getMessage() { return message; } public void setMessage(String message) { this.message = message; } public Date getSendTime() { return sendTime; } public void setSendTime(Date sendTime) { this.sendTime = sendTime; } public String getNodeName() { return NodeName; } public void setNodeName(String nodeName) { NodeName = nodeName; } public List<Integer> getIntList() { return intList; } public void setIntList(List<Integer> intList) { this.intList = intList; } @Override public String toString() { return "XwjUser [id=" + id + ", message=" + message + ", sendTime=" + sendTime + ", intList=" + intList + "]"; } }
先创建一个ObjectMapper,然后赋值一些属性:
public static ObjectMapper mapper = new ObjectMapper(); static { // 转换为格式化的json mapper.enable(SerializationFeature.INDENT_OUTPUT); // 如果json中有新增的字段并且是实体类类中不存在的,不报错 mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false); }
1、对象与json字符串、byte数组
@Test public void testObj() throws JsonGenerationException, JsonMappingException, IOException { XwjUser user = new XwjUser(1, "Hello World", new Date()); mapper.writeValue(new File("D:/test.txt"), user); // 写到文件中 // mapper.writeValue(System.out, user); //写到控制台 String jsonStr = mapper.writeValueAsString(user); System.out.println("对象转为字符串:" + jsonStr); byte[] byteArr = mapper.writeValueAsBytes(user); System.out.println("对象转为byte数组:" + byteArr); XwjUser userDe = mapper.readValue(jsonStr, XwjUser.class); System.out.println("json字符串转为对象:" + userDe); XwjUser useDe2 = mapper.readValue(byteArr, XwjUser.class); System.out.println("byte数组转为对象:" + useDe2); }
运行结果:
对象转为字符串:{ "id" : 1, "message" : "Hello World", "sendTime" : 1525163446305, "intList" : null, "nodeName" : null } 对象转为byte数组:[B@3327bd23 json字符串转为对象:XwjUser [id=1, message=Hello World, sendTime=Tue May 01 16:30:46 CST 2018, intList=null] byte数组转为对象:XwjUser [id=1, message=Hello World, sendTime=Tue May 01 16:30:46 CST 2018, intList=null]
注意,对象转json字符串时,对象中的NodeName首字母是大写,转出来是小写
2、list集合与json字符串
@Test public void testList() throws JsonGenerationException, JsonMappingException, IOException { List<XwjUser> userList = new ArrayList<>(); userList.add(new XwjUser(1, "aaa", new Date())); userList.add(new XwjUser(2, "bbb", new Date())); userList.add(new XwjUser(3, "ccc", new Date())); userList.add(new XwjUser(4, "ddd", new Date())); String jsonStr = mapper.writeValueAsString(userList); System.out.println("集合转为字符串:" + jsonStr); List<XwjUser> userListDes = mapper.readValue(jsonStr, List.class); System.out.println("字符串转集合:" + userListDes); }
运行结果:
集合转为字符串:[ { "id" : 1, "message" : "aaa", "sendTime" : 1525164096846, "intList" : null, "nodeName" : null }, { "id" : 2, "message" : "bbb", "sendTime" : 1525164096846, "intList" : null, "nodeName" : null }, { "id" : 3, "message" : "ccc", "sendTime" : 1525164096846, "intList" : null, "nodeName" : null }, { "id" : 4, "message" : "ddd", "sendTime" : 1525164096846, "intList" : null, "nodeName" : null } ] 字符串转集合:[{id=1, message=aaa, sendTime=1525164096846, intList=null, nodeName=null}, {id=2, message=bbb, sendTime=1525164096846, intList=null, nodeName=null}, {id=3, message=ccc, sendTime=1525164096846, intList=null, nodeName=null}, {id=4, message=ddd, sendTime=1525164096846, intList=null, nodeName=null}]
3、map与json字符串
@SuppressWarnings("unchecked") @Test public void testMap() { Map<String, Object> testMap = new HashMap<>(); testMap.put("name", "merry"); testMap.put("age", 30); testMap.put("date", new Date()); testMap.put("user", new XwjUser(1, "Hello World", new Date())); try { String jsonStr = mapper.writeValueAsString(testMap); System.out.println("Map转为字符串:" + jsonStr); try { Map<String, Object> testMapDes = mapper.readValue(jsonStr, Map.class); System.out.println("字符串转Map:" + testMapDes); } catch (IOException e) { e.printStackTrace(); } } catch (JsonProcessingException e) { e.printStackTrace(); } }
运行结果:
Map转为字符串:{ "date" : 1525164199804, "name" : "merry", "user" : { "id" : 1, "message" : "Hello World", "sendTime" : 1525164199805, "intList" : null, "nodeName" : null }, "age" : 30 } 字符串转Map:{date=1525164199804, name=merry, user={id=1, message=Hello World, sendTime=1525164199805, intList=null, nodeName=null}, age=30}
4、修改转换时的日期格式:
@Test public void testOther() throws IOException { // 修改时间格式 mapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")); XwjUser user = new XwjUser(1, "Hello World", new Date()); user.setIntList(Arrays.asList(1, 2, 3)); String jsonStr = mapper.writeValueAsString(user); System.out.println("对象转为字符串:" + jsonStr); }
运行结果:
对象转为字符串:{ "id" : 1, "message" : "Hello World", "sendTime" : "2018-05-01 16:44:06", "intList" : [ 1, 2, 3 ], "nodeName" : null }
本文来自博客园,作者:aspirant,转载请注明原文链接:https://www.cnblogs.com/aspirant/p/11459148.html