Json解析工具Jackson（使用注解）

素颜马尾好姑娘i 2021-09-26 01:04 484阅读 0赞

接上一篇文章[Json解析工具Jackson（简单应用）][Json_Jackson]，jackson在实际应用中给我们提供了一系列注解，提高了开发的灵活性，下面介绍一下最常用的一些注解

*  @JsonIgnoreProperties

此注解是类注解，作用是json序列化时将[Java ][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），作用和上面的@JsonIgnoreProperties一样。

*  @JsonFormat

此注解用于属性或者方法上（最好是属性上），可以方便的把Date类型直接转化为我们想要的模式，比如@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我们自定义的代码，比如序列化一个double时在其后面限制两位小数点。

package com.xiaowu.jackson.anno;
    
    import java.io.IOException;
    import java.text.DecimalFormat;
    
    import com.fasterxml.jackson.core.JsonGenerator;
    import com.fasterxml.jackson.core.JsonProcessingException;
    import com.fasterxml.jackson.databind.JsonSerializer;
    import com.fasterxml.jackson.databind.SerializerProvider;
    
    /**
     * 
     * @author xiaowu
     *
     */
    public class CustomDoubleSerialize extends JsonSerializer<Double>{
    	
    	private DecimalFormat dec = new DecimalFormat("##.00");
    
    	/**
    	 * @param JsonGenerator  json流输出
    	 */
    	public void serialize(Double value, JsonGenerator jgen,
    			SerializerProvider provider) throws IOException,
    			JsonProcessingException {
    		// TODO Auto-generated method stub
    		jgen.writeString(dec.format(value));
    		
    	}
    
    }

*  @JsonDeserialize

此注解用于属性或者setter方法上，用于在反序列化时可以嵌入我们自定义的代码，类似于上面的@JsonSerialize

package com.xiaowu.jackson.anno;
    
    import java.io.IOException;
    import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.util.Date;
    
    import com.fasterxml.jackson.core.JsonParser;
    import com.fasterxml.jackson.core.JsonProcessingException;
    import com.fasterxml.jackson.databind.DeserializationContext;
    import com.fasterxml.jackson.databind.JsonDeserializer;
    
    /**
     * 
     * @author xiaowu
     *
     */
    public class CustomDateDeserialize extends JsonDeserializer<Date>{
    	
    	private SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmss");
    
    	public Date deserialize(JsonParser jp, DeserializationContext ctxt)
    			throws IOException, JsonProcessingException {
    		// TODO Auto-generated method stub
    		Date date = null;
    		//String s1 = null;
    		try {
    			date = sdf.parse(jp.getText());
    			//s1 = sdf.format(date);
    		} catch (ParseException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    		return date;
    	}
    
    }

完整代码：

package com.xiaowu.jackson.anno;
    
    import java.util.Date;
    
    import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
    import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
    import com.fasterxml.jackson.databind.annotation.JsonSerialize;
    
    /**
     * 
     * @author xiaowu
     *
     */
    //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, 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 + "]";  
        }  
    
    }

package com.xiaowu.jackson.anno;
    
    import java.io.File;
    import java.io.IOException;
    import java.util.Date;
    
    import org.junit.Test;
    
    import com.fasterxml.jackson.core.JsonGenerationException;
    import com.fasterxml.jackson.core.JsonParseException;
    import com.fasterxml.jackson.databind.JsonMappingException;
    import com.fasterxml.jackson.databind.ObjectMapper;
    
    /**
     * 
     * @author xiaowu
     *
     */
    public class demo {
    	
    	 // 直接写入一个对象(所谓序列化)  
    	@Test
        public 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("d:/person.json"), person);
    		} catch (JsonGenerationException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		} catch (JsonMappingException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		} catch (IOException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
        	
        }
    	
    	// 直接将一个json转化为对象（所谓反序列化）  
    	@Test
        public void readJsonObject() {  
            ObjectMapper mapper = new ObjectMapper();  
      
            try {  
                Person person = mapper.readValue(new File("d:/person.json"),  
                        Person.class);  
                System.out.println(person.toString());  
            } catch (JsonParseException e) {  
                e.printStackTrace();  
            } catch (JsonMappingException e) {  
                e.printStackTrace();  
            } catch (IOException e) {  
                e.printStackTrace();  
            }  
        }  
    
    }

[Json_Jackson]: http://blog.csdn.net/jinwufeiyang/article/details/52795713
[Java]: http://lib.csdn.net/base/java