Jackson 反序列化为List

使用Jackson 如何把json字符串反序列化为List呢?
(List中是自定义对象)
先看下常规的反序列化:

@Test    public void test_reserialize(){        String jsonInput = "{\"addrr\":{\"country\":\"中国\",\"state\":\"湖北省\",\"street\":\"清河\"},\"age\":25,\"hobby\":\"\",\"name\":\"黄威\"}";        ObjectMapper mapper = new ObjectMapper();        Student student;        try {            student = mapper.readValue(jsonInput, Student.class);            System.out.println(student.getAddrr().getStreet());            System.out.println(student.getName());        } catch (Exception e) {            e.printStackTrace();        }    }

运行结果:

序列化

@Test    public void test_004(){        List<Teacher> list=new ArrayList<Teacher>();        Teacher t=new Teacher();        t.setId(2);        t.setName("雄鹰表");        t.setTitle("aa");        list.add(t);        t=new Teacher();        t.setId(3);        t.setName("陈定生");        t.setTitle("bb");        list.add(t);        t=new Teacher();        t.setId(4);        t.setName("张阿勇");        t.setTitle("cc");        list.add(t);        ObjectMapper mapper = new ObjectMapper();        String content;        try {            content = mapper.writeValueAsString(list);            System.out.println(content);        } catch (JsonGenerationException e) {            e.printStackTrace();        } catch (JsonMappingException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }

运行结果:
[{“id”:2,”title”:”aa”,”name”:”雄鹰表”},{“id”:3,”title”:”bb”,”name”:”陈定生”},{“id”:4,”title”:”cc”,”name”:”张阿勇”}]

反序列化
把上述json字符串反序列化为List
代码如下:

@Test    public void test_006(){        String jsonInput="[{\"id\":2,\"title\":\"aa\",\"name\":\"雄鹰表\"},{\"id\":3,\"title\":\"bb\",\"name\":\"陈定生\"},{\"id\":4,\"title\":\"cc\",\"name\":\"张阿勇\"}]";        ObjectMapper mapper = new ObjectMapper();        List student;        try {            student = mapper.readValue(jsonInput, List.class);            System.out.println(student.size());        } catch (Exception e) {            e.printStackTrace();        }    }

运行时

没有达到预期效果,虽然反序列化成了List,但是并不是List< Teacher>,而是List< HashMap>
如何解决这个问题呢?
解决方法:使用mapper.getTypeFactory().constructParametricType

 /**        * 获取泛型的Collection Type       * @param collectionClass 泛型的Collection        * @param elementClasses 元素类        * @return JavaType Java类型        * @since 1.0        */    public static JavaType getCollectionType(ObjectMapper mapper,Class<?> collectionClass, Class<?>... elementClasses) {        return mapper.getTypeFactory().constructParametricType(collectionClass, elementClasses);    }    @Test    public void test_006(){        String jsonInput="[{\"id\":2,\"title\":\"aa\",\"name\":\"雄鹰表\"},{\"id\":3,\"title\":\"bb\",\"name\":\"陈定生\"},{\"id\":4,\"title\":\"cc\",\"name\":\"张阿勇\"}]";        ObjectMapper mapper = new ObjectMapper();        List student;        try {            student = mapper.readValue(jsonInput, getCollectionType(mapper, List.class, Teacher.class));            System.out.println(student.size());        } catch (Exception e) {            e.printStackTrace();        }    }

参考:Jackson将json字符串转换成泛型List