利用Jackson處理json需要匯入的jar包（2以上版本的）：

<dependency>
     <groupId>com.fasterxml.jackson.core</groupId>
     <artifactId>jackson-core</artifactId>
     <version>2.3.3</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.3.3</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
    <version>2.3.3</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.dataformat</groupId>
    <artifactId>jackson-dataformat-smile</artifactId>
    <version>2.3.3</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.jaxrs</groupId>
    <artifactId>jackson-jaxrs-json-provider</artifactId>
    <version>2.3.3</version>
</dependency>
<!-- Support for JAX-B annotations as additional configuration -->
<dependency>
    <groupId>com.fasterxml.jackson.module</groupId>
    <artifactId>jackson-module-jaxb-annotations</artifactId>
    <version>2.3.3</version>
</dependency>
 

測試程式碼：

@Test
	public void writeEntity2JSON() throws JsonProcessingException, IOException {
		ObjectMapper objectMapper = new ObjectMapper();
		Person person = new Person();
		person.setId(1);
		person.setName("zhangsan");
		person.setEmail("[email protected]");
	       /**
          * ObjectMapper是JSON操作的核心，Jackson的所有JSON操作都是在ObjectMapper中實現。
          * ObjectMapper有多個JSON序列化的方法，可以把JSON字串儲存File、OutputStream等不同的介質中。
          * writeValue(File file, Object arg1)把arg1轉成json序列，並儲存到file檔案中。
          * writeValue(OutputStream out, Object arg1)把arg1轉成json序列，並儲存到out輸出流中。
          * writeValueAsBytes(Object arg0)把arg0轉成json序列，並把結果輸出成位元組陣列。
          * writeValueAsString(Object arg0)把arg0轉成json序列，並把結果輸出成字串。
          */
		String jsonStr=objectMapper.writeValueAsString(person);
                System.out.println(jsonStr);
 }

	@Test
	public void readJson2Entity() throws JsonParseException, JsonMappingException, IOException {
		ObjectMapper objectMapper = new ObjectMapper();
		String json = "{\"id\":1,\"name\":\"haha\",\"email\":\"email\"}";
		Person acc = objectMapper.readValue(json, Person.class);
		System.out.println(acc);
	}

	@Test
	public void readJson2Map() throws JsonParseException, JsonMappingException, IOException {
		ObjectMapper objectMapper = new ObjectMapper();
		String json = "{\"A\":{\"id\":1,\"name\":\"zhangsan\",\"email\":\"
 
[email protected]\"},\"B\":{\"id\":2,\"name\":\"lisi\",\"email\":\"[email protected]\"},\"success\":true}";
		@SuppressWarnings("unchecked")
		Map<String, Map<String, Object>> maps = objectMapper.readValue(json, Map.class);
		System.out.println(maps);
	}

	@Test
	public void readJson2List() throws IOException {
		ObjectMapper objectMapper = new ObjectMapper();
		String json = "[{\"id\":1,\"name\":\"zhangsan\",\"email\":\"
 
[email protected]\"},{\"id\":2,\"name\":\"lisi\",\"email\":\"[email protected]\"}]";
		@SuppressWarnings("unchecked")
		List<LinkedHashMap<String, Object>> list = objectMapper.readValue(json, List.class);
		System.out.println(list);
	}

	@Test
	public void readJson2Array() throws JsonParseException, JsonMappingException, IOException {
		ObjectMapper objectMapper = new ObjectMapper();
		String json = "[{\"id\":1,\"name\":\"zhangsan\",\"email\":\"[email protected]\"},{\"id\":2,\"name\":\"lisi\",\"email\":\"[email protected]\"}]";
		Person[] arr = objectMapper.readValue(json, Person[].class);
		System.out.println(arr.length);
	}

其實主要用到了兩個方法：

轉換成json物件或者說json字串時，用objectMapper的writeValueAsString()方法或是writeValue()過載方法(objectMapper只需通過無參構造器new出來)

轉換json字串時用objectMapperd的readValue(String content, Class<T> valueType)，直接得到JavaBean物件，中間並沒有轉換成Json物件環節。

一個writeValueAsString()，一個是readValue()，對應的，很好記。