Jackson第一篇【JSON字符串、实体之间的相互转换】
既然你看到这篇文章相信你已经了解JSON的好处了，那么废话不多说直接进入主题。
Jackson是java中众多json处理工具的一个，比起常见的Json-lib,Gson要快一些。
Jackson的官网：http://jackson.codehaus.org/
里面可以下载Jackson的Jar包? 注意jackson依赖：Apache的commons-loggin。
下面聊一下Jackson的常见用法==================================
Bean----->JSON
public static String beanToJson(Object obj) throws IOException {// 这里异常都未进行处理，而且流的关闭也不规范。开发中请勿这样写，如果发生异常流关闭不了ObjectMapper mapper = CommonUtil.getMapperInstance(false);StringWriter writer = new StringWriter();JsonGenerator gen = new JsonFactory().createJsonGenerator(writer);mapper.writeValue(gen, obj);gen.close();String json = writer.toString();writer.close();return json;}JSON------>Bean?
public static Object jsonToBean(String json, Class<?> cls) throws Exception {Object vo = mapper.readValue(json, cls);return vo;}?
好了方法写完了咱们测试一下吧 看看他是否支持复杂类型的转换
public static void main(String[] args) throws Exception {// 准备数据List<Person> pers = new ArrayList<Person>();Person p = new Person("张三", 46);pers.add(p);p = new Person("李四", 19);pers.add(p);p = new Person("王二麻子", 23);pers.add(p);TestVo vo = new TestVo("一个容器而已", pers);// 实体转JSON字符串String json = beanToJson(vo);System.out.println("Bean>>>Json----" + json);// 字符串转实体TestVo vo2 = (TestVo)jsonToBean(json, TestVo.class);System.out.println("Json>>Bean--与开始的对象是否相等：" + vo2.equals(vo));}?输出结果
Bean>>>Json----{"voName":"一个容器而已","pers":[{"name":"张三","age":46},{"name":"李四","age":19},{"name":"王二麻子","age":23}]}
Json>>Bean--与开始的对象是否相等：true
从结果可以看出从咱们转换的方法是对的，本文只是对Jackson的一个最简单的使用介绍。接下来的几篇文章咱们深入研究一下这玩意到底有多强大！
?
?
下面是本人涉及到的Bean 以及 CommonUtil
?
public class CommonUtil {private static ObjectMapper mapper;/** * 一个破ObjectMapper而已，你为什么不直接new 还搞的那么复杂。接下来的几篇文章我将和你一起研究这个令人蛋疼的问题 * * @param createNew * 是否创建一个新的Mapper * @return */public static synchronized ObjectMapper getMapperInstance(boolean createNew) {if (createNew) {return new ObjectMapper();} else if (mapper == null) {mapper = new ObjectMapper();}return mapper;}}?
?
public class Person {private String name;private int age;public Person() {}public Person(String name, int age) {super();this.name = name;this.age = age;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}@Overridepublic boolean equals(Object obj) {if (this == obj) {return true;}if (obj == null) {return false;}if (getClass() != obj.getClass()) {return false;}Person other = (Person) obj;if (age != other.age) {return false;}if (name == null) {if (other.name != null) {return false;}} else if (!name.equals(other.name)) {return false;}return true;}}public class TestVo {private String voName;private List<Person> pers;public TestVo() {}public TestVo(String voName, List<Person> pers) {super();this.voName = voName;this.pers = pers;}public String getVoName() {return voName;}public void setVoName(String voName) {this.voName = voName;}public List<Person> getPers() {return pers;}public void setPers(List<Person> pers) {this.pers = pers;}@Overridepublic boolean equals(Object obj) {if (this == obj) {return true;}if (obj == null) {return false;}if (getClass() != obj.getClass()) {return false;}TestVo other = (TestVo) obj;if (pers == null) {if (other.pers != null) {return false;}} else if (pers.size() != other.pers.size()) {return false;} else {for (int i = 0; i < pers.size(); i++) {if (!pers.get(i).equals(other.pers.get(i))) {return false;}}}if (voName == null) {if (other.voName != null) {return false;}} else if (!voName.equals(other.voName)) {return false;}return true;}}?
?
?
?
?
万分感谢楼主，刚好项目中遇到JSON->Bean的问题。谢谢分享！！ 3 楼 shuguang1108 2012-06-01 楼主，我想请教下：如何实现类似 JSON字符串与List<Person>、Map<Integer,String>、Map<Integer,Person>等集合类型之间的相互转换呢？ 急求帮助~