日期:2014-05-16  浏览次数:20358 次

利用Jackson对Object,Map,List,数组,枚举,日期类等转化为json
利用Jackson中的ObjectMapper对象,转为对象为json字符串,springside对Jackson的简单封装 JsonBinder :
public class JsonBinder {

	private static Logger logger = LoggerFactory.getLogger(JsonBinder.class);

	private ObjectMapper mapper;

	public JsonBinder(Inclusion inclusion) {
		mapper = new ObjectMapper();
		//设置输出包含的属性
		mapper.getSerializationConfig().setSerializationInclusion(inclusion);
		//设置输入时忽略JSON字符串中存在而Java对象实际没有的属性
		mapper.getDeserializationConfig().set(
				org.codehaus.jackson.map.DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
	}

	/**
	 * 创建输出全部属性到Json字符串的Binder.
	 */
	public static JsonBinder buildNormalBinder() {
		return new JsonBinder(Inclusion.ALWAYS);
	}

	/**
	 * 创建只输出非空属性到Json字符串的Binder.
	 */
	public static JsonBinder buildNonNullBinder() {
		return new JsonBinder(Inclusion.NON_NULL);
	}

	/**
	 * 创建只输出初始值被改变的属性到Json字符串的Binder.
	 */
	public static JsonBinder buildNonDefaultBinder() {
		return new JsonBinder(Inclusion.NON_DEFAULT);
	}

	/**
	 * 如果JSON字符串为Null或"null"字符串,返回Null.
	 * 如果JSON字符串为"[]",返回空集合.
	 * 
	 * 如需读取集合如List/Map,且不是List<String>这种简单类型时使用如下语句:
	 * List<MyBean> beanList = binder.getMapper().readValue(listString, new TypeReference<List<MyBean>>() {});
	 */
	public <T> T fromJson(String jsonString, Class<T> clazz) {
		if (StringUtils.isEmpty(jsonString)) {
			return null;
		}

		try {
			return mapper.readValue(jsonString, clazz);
		} catch (IOException e) {
			logger.warn("parse json string error:" + jsonString, e);
			return null;
		}
	}

	/**
	 * 如果对象为Null,返回"null".
	 * 如果集合为空集合,返回"[]".
	 */
	public String toJson(Object object) {

		try {
			return mapper.writeValueAsString(object);
		} catch (IOException e) {
			logger.warn("write to json string error:" + object, e);
			return null;
		}
	}

	/**
	 * 设置转换日期类型的format pattern,如果不设置默认打印Timestamp毫秒数.
	 */
	public void setDateFormat(String pattern) {
		if (StringUtils.isNotBlank(pattern)) {
			DateFormat df = new SimpleDateFormat(pattern);
			mapper.getSerializationConfig().setDateFormat(df);
			mapper.getDeserializationConfig().setDateFormat(df);
		}
	}

	/**
	 * 取出Mapper做进一步的设置或使用其他序列化API.
	 */
	public ObjectMapper getMapper() {
		return mapper;
	}
}


在其他类中定义jsonBinder对象:
private static JsonBinder binder = JsonBinder.buildNonDefaultBinder();


以下是对象到json字符串以及json字符串到对象的转化:
/**
	 * 序列化对象/集合到Json字符串.
	 */
	@Test
	public void toJson() throws Exception {
		//Bean
		TestBean bean = new TestBean("A");
		String beanString = binder.toJson(bean);
		System.out.println("Bean:" + beanString);
		assertEquals("{\"name\":\"A\"}", beanString);

		//Map
		Map<String, Object> map = Maps.newLinkedHashMap();
		map.put("name", "A");
		map.put("age", 2);
		String mapString = binder.toJson(map);
		System.out.println("Map:" + mapString);
		assertEquals("{\"name\":\"A\",\"age\":2}", mapString);

		//List<String>
		List<String> stringList = Lists.newArrayList("A", "B", "C");
		String listString = binder.toJson(stringList);
		System.out.println("String List:" + listString);
		assertEquals("[\"A\",\"B\",\"C\"]", listString);

		//List<Bean>
		List<TestBean> beanList = Lists.newArrayList(new TestBean("A"), new TestBean("B"));
		String beanListString = binder.toJson(beanList);
		System.out.println("Bean List:" + beanListString);
		assertEquals("[{\"name\":\"A\"},{\"name\":\"B\"}]", beanListString);

		//Bean[]
		TestBean[] beanArray = new TestBean[] { new TestBean("A"), new TestBean("B") };
		String beanArrayString = binder.toJson(beanArray);
		System.out.println("Array List:" + beanArrayString);
		assertEquals("[{\"name\":\"A\"},{\"name\":\"B\"}]", beanArrayString);
	}

	/**
	 * 从Json字符串反序列化对象/集合.
	 */
	@Test
	@SuppressWarnings("unchecked")
	public void fromJson() throws Exception {
		//Bean
		String beanString = "{\"name\":\"A\"