利用jackson对object,map,list,数组,枚举,日期类等转化为json -买球官网平台

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这种简单类型时使用如下语句:
	 * list beanlist = binder.getmapper().readvalue(liststring, new typereference>() {});
	 */
	public  t fromjson(string jsonstring, class 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 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
		list stringlist = lists.newarraylist("a", "b", "c");
		string liststring = binder.tojson(stringlist);
		system.out.println("string list:"   liststring);
		assertequals("[\"a\",\"b\",\"c\"]", liststring);
		//list
		list 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\"}";
		testbean bean = binder.fromjson(beanstring, testbean.class);
		system.out.println("bean:"   bean);
		//map
		string mapstring = "{\"name\":\"a\",\"age\":2}";
		map map = binder.fromjson(mapstring, hashmap.class);
		system.out.println("map:");
		for (entry entry : map.entryset()) {
			system.out.println(entry.getkey()   " "   entry.getvalue());
		}
		//list
		string liststring = "[\"a\",\"b\",\"c\"]";
		list stringlist = binder.getmapper().readvalue(liststring, list.class);
		system.out.println("string list:");
		for (string element : stringlist) {
			system.out.println(element);
		}
		//list
		string beanliststring = "[{\"name\":\"a\"},{\"name\":\"b\"}]";
		list beanlist = binder.getmapper().readvalue(beanliststring, new typereference>() {
		});
		system.out.println("bean list:");
		for (testbean element : beanlist) {
			system.out.println(element);
		}
	}

在我的实际项目中，遇到一个有意思的问题，我把一个对象转为为json字符串时，调用binder.tojson(bean) ，这个方法，方法总是返回null，后面发现该bean中没有默认的构造函数，加上某人构造函数就ok了。