Jackson-将对象转为Json字符串

SpringMVC-处理JSON

1、引入jackson依赖

  <properties>
    <jackson.version>1.9.13</jackson.version>
  </properties>
  <dependencies>
     <!-- json和bean之间相互转换 -->
    <dependency>
      <groupId>org.codehaus.jackson</groupId>
      <artifactId>jackson-core-asl</artifactId>
      <version>${jackson.version}</version>
    </dependency>
    <dependency>
      <groupId>org.codehaus.jackson</groupId>
      <artifactId>jackson-mapper-asl</artifactId>
      <version>${jackson.version}</version>
    </dependency>
  </dependencies>

2、具体使用步骤

①、创建org.codehaus.jackson.map,ObjectMapper对象

②、调用ObjectMapper的writerValueAsString 方法把Java对象或集合转为JSON字符串

3、Demo

import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.annotate.JsonIgnore;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;

import java.io.IOException;
import java.util.Arrays;
import java.util.List;

public class Customer {
    private String name;
    private String id;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public Customer(String name, String id) {
        super();
        this.name = name;
        this.id = id;
    }
    public String getCity(){
        return "beijing";
    }
    @JsonIgnore
    public String getBirthday(){
        return "1980-12-12";
    }
    public static void main(String[] args) throws JsonGenerationException, JsonMappingException, IOException {
        //1.导入jar包
        //2.创建objectmappter对象
        ObjectMapper mapper=new ObjectMapper();
        //3.调用mapper的writeValueAsString()方法把一个对象或集合转为json字符串
        Customer customer=new Customer("aaa", "333");
        String jsonStr=mapper.writeValueAsString(customer);
        System.out.println(jsonStr);
        //4.注意：jackson使用getter方法来定位json对象的属性
        //5.可以通过添加注解JsonIgnore忽略某一个getter定义的属性
        List<Customer> customers=Arrays.asList(customer,new Customer("bb", "213"));
        jsonStr=mapper.writeValueAsString(customers);
        System.out.println(jsonStr);
    }
}

控制台结果

{"name":"aaa","id":"333","city":"beijing"}
[{"name":"aaa","id":"333","city":"beijing"},{"name":"bb","id":"213","city":"beijing"}]

4、注意点

①、JackSon 根据getter 来定位Json 对象的属性，而不是字段

②、可以在类的getter方法上添加注解：

org.codehaus.jackson.annotate.JsonIgnore

在转为Json对象是以忽略该属性