Question

public class Parent {

    private List<Child> childs;

}

public class Parent {

    private Set<Child> childs;

}

@RequestMapping(value = "/save", method = RequestMethod.POST)
public void saveFooter(@RequestBody Parent parent, Model model)

下面的

是示例JSON对象。

{child: [{ name: 'a'}, { name: 'b'}]}

当我在Parent.class parent.getChilds.size()中对子项使用设置时，子项的大小仅为1（这是错误的）。

但是当我在Parent.class parent.getChilds.size()中使用列表作为子项时，子项的大小为2（这是正确的）

编辑：

public class Child {

    private String name;

}

jackson maven依赖

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.4</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-annotations</artifactId>
            <version>2.4</version>
        </dependency>

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.4</version>
        </dependency>

        <dependency>
            <groupId>com.fasterxml.jackson.datatype</groupId>
            <artifactId>jackson-datatype-hibernate4</artifactId>
            <version>2.4</version>
        </dependency>

编辑：

public class Child {
    private Long id;
    private String name;

    @Override
    public boolean equals(final Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        final Child other = (Child) obj;
        if (id == null) {
            if (other.id != null)
                return false;
        } else if (!id.equals(other.id))
            return false;
        return true;
    } 
}

发现问题是由于我实现了Child.class的equals方法这使得两个物体相等。

Answer 1

<强> Parent.java

package com.test;

import java.util.Set;

public class Parent {

    private Set<Child> childs;

    public Set<Child> getChilds() {
        return childs;
    }

    public void setChilds(Set<Child> childs) {
        this.childs = childs;
    }
}

<强> Child.Java

package com.test;

public class Child {
    private String name;

    public Child(String name) {
        this.name = name;
    }

    public Child() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

<强> Test.java

    package com.test;

import java.io.IOException;
import java.util.HashSet;

import org.codehaus.jackson.JsonParseException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;

import flexjson.JSONSerializer;

public class MvelCompilation {

    public static void main(String[] args) {

        Parent parent = new Parent();
        Child c1 = new Child("Ankur1");
        Child c2 = new Child("Ankur2");

        HashSet<Child> childSet = new HashSet<Child>();
        childSet.add(c1);
        childSet.add(c2);
        parent.setChilds(childSet);

        JSONSerializer serializer = new JSONSerializer();
        System.out.println("Json String is = " + serializer.exclude("*.class").deepSerialize(parent));

        String s = "{\"childs\":[{\"name\":\"Ankur1\"},{\"name\":\"Ankur2\"}]}";

        try {
            Parent parent1 = new ObjectMapper().readValue(s, Parent.class);
            System.out.println("size = " + parent1.getChilds().size());
        } catch (JsonParseException 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();
        }

    }
}

<强>输出

Json String = {“childs”：[{“name”：“Ankur1”}，{“name”：“Ankur2”}}}

size = 2

无法使用Spring MVC / jackson将JSON序列化为正确设置

1 个答案: