Json解析工具Jackson（使用注解）

http://blog.csdn.net/nomousewch/article/details/8955796

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       接上一篇文章Json解析工具Jackson（简单应用），jackson在实际应用中给咱们提供了一系列注解，提升了开发的灵活性，下面介绍一下最经常使用的一些注解

• @JsonIgnoreProperties

         此注解是类注解，做用是json序列化时将java bean中的一些属性忽略掉，序列化和反序列化都受影响。

• @JsonIgnore

         此注解用于属性或者方法上（最好是属性上），做用和上面的@JsonIgnoreProperties同样。

• @JsonFormat

        此注解用于属性或者方法上（最好是属性上），能够方便的把Date类型直接转化为咱们想要的模式，好比@JsonFormat(pattern = "yyyy-MM-dd HH-mm-ss")

• @JsonSerialize

        此注解用于属性或者getter方法上，用于在序列化时嵌入咱们自定义的代码，好比序列化一个double时在其后面限制两位小数点。

    public class CustomDoubleSerialize extends JsonSerializer<Double> {  
      
        private DecimalFormat df = new DecimalFormat("##.00");  
      
        @Override  
        public void serialize(Double value, JsonGenerator jgen,  
                SerializerProvider provider) throws IOException,  
                JsonProcessingException {  
      
            jgen.writeString(df.format(value));  
        }  
    }  

• @JsonDeserialize

         此注解用于属性或者setter方法上，用于在反序列化时能够嵌入咱们自定义的代码，相似于上面的@JsonSerialize

    public class CustomDateDeserialize extends JsonDeserializer<Date> {  
      
        private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");  
      
        @Override  
        public Date deserialize(JsonParser jp, DeserializationContext ctxt)  
                throws IOException, JsonProcessingException {  
      
            Date date = null;  
            try {  
                date = sdf.parse(jp.getText());  
            } catch (ParseException e) {  
                e.printStackTrace();  
            }  
            return date;  
        }  
    }  

完整例子

    //表示序列化时忽略的属性  
    @JsonIgnoreProperties(value = { "word" })  
    public class Person {  
        private String name;  
        private int age;  
        private boolean sex;  
        private Date birthday;  
        private String word;  
        private double salary;  
      
        public String getName() {  
            return name;  
        }  
      
        public void setName(String name) {  
            this.name = name;  
        }  
      
        public int getAge() {  
            return age;  
        }  
      
        public void setAge(int age) {  
            this.age = age;  
        }  
      
        public boolean isSex() {  
            return sex;  
        }  
      
        public void setSex(boolean sex) {  
            this.sex = sex;  
        }  
      
        public Date getBirthday() {  
            return birthday;  
        }  
      
        // 反序列化一个固定格式的Date  
        @JsonDeserialize(using = CustomDateDeserialize.class)  
        public void setBirthday(Date birthday) {  
            this.birthday = birthday;  
        }  
      
        public String getWord() {  
            return word;  
        }  
      
        public void setWord(String word) {  
            this.word = word;  
        }  
      
        // 序列化指定格式的double格式  
        @JsonSerialize(using = CustomDoubleSerialize.class)  
        public double getSalary() {  
            return salary;  
        }  
      
        public void setSalary(double salary) {  
            this.salary = salary;  
        }  
      
        public Person(String name, int age) {  
            this.name = name;  
            this.age = age;  
        }  
      
        public Person(String name, int age, boolean sex, Date birthday,  
                String word, double salary) {  
            super();  
            this.name = name;  
            this.age = age;  
            this.sex = sex;  
            this.birthday = birthday;  
            this.word = word;  
            this.salary = salary;  
        }  
      
        public Person() {  
        }  
      
        @Override  
        public String toString() {  
            return "Person [name=" + name + ", age=" + age + ", sex=" + sex  
                    + ", birthday=" + birthday + ", word=" + word + ", salary="  
                    + salary + "]";  
        }  
      
    }  

    public class Demo {  
        public static void main(String[] args) {  
      
            writeJsonObject();  
      
            // readJsonObject();  
        }  
      
        // 直接写入一个对象(所谓序列化)  
        public static void writeJsonObject() {  
            ObjectMapper mapper = new ObjectMapper();  
            Person person = new Person("nomouse", 25, true, new Date(), "程序员",  
                    2500.0);  
            try {  
                mapper.writeValue(new File("c:/person.json"), person);  
            } catch (JsonGenerationException e) {  
                e.printStackTrace();  
            } catch (JsonMappingException e) {  
                e.printStackTrace();  
            } catch (IOException e) {  
                e.printStackTrace();  
            }  
        }  
      
        // 直接将一个json转化为对象（所谓反序列化）  
        public static void readJsonObject() {  
            ObjectMapper mapper = new ObjectMapper();  
      
            try {  
                Person person = mapper.readValue(new File("c:/person.json"),  
                        Person.class);  
                System.out.println(person.toString());  
            } catch (JsonParseException e) {  
                e.printStackTrace();  
            } catch (JsonMappingException e) {  
                e.printStackTrace();  
            } catch (IOException e) {  
                e.printStackTrace();  
            }  
        }  
      
      
    }