FastJson的常用操作

FastJson的常用操作

2017-06-05

常用操作包括以下内容：

1. 对象与（JsonObject或JsonArray）与String的互换
2. String转换为（JsonObject或JsonArray）如何保持顺序
3. Eval的使用
4. 值为null的（JsonObject或JsonArray）转换为String时如何保存

代码：

package Demo.Sample1;
import com.alibaba.fastjson.JSON;

import com.alibaba.fastjson.JSONPath;

import com.alibaba.fastjson.parser.Feature;

import com.alibaba.fastjson.serializer.SerializerFeature;
public class Sample {
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> main(String[] args) {
    
    Group group </span>=<span style="color: #000000;"> GenerateGroup();
    String ss</span>="{"id":1.1,"name":"admin","users":[{"id":2.2,"name":"guest"},{"id":3.3,"name":"root"}]}"<span style="color: #000000;">;        
    Group groupWithNull</span>=<span style="color: #000000;">GenerateGroupWithNull();
    
    BasicObjectToStringCompare();
    JsonObjectToStringCompare(ss);
    NJsonObjectToStringCompare(group);
    JsonStringSequence(group, ss);        
    JsonEval(ss,</span>"$.users"<span style="color: #000000;">);
    DealWithNullToStringString(groupWithNull);        
}

</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> BasicObjectToStringCompare()
{
    System.out.println(</span>"---------- 基元类型 toString() toJSONString() 比较: ----------"<span style="color: #000000;">);
    System.out.println(</span>"ZifuChuan"<span style="color: #000000;">);
    System.out.println(JSON.toJSONString(</span>"ZifuChuan"<span style="color: #000000;">));
    System.out.println(</span><span style="color: #0000ff;">true</span><span style="color: #000000;">);
    System.out.println(JSON.toJSONString(</span><span style="color: #0000ff;">true</span><span style="color: #000000;">));
    System.out.println(</span>1.1<span style="color: #000000;">);
    System.out.println(JSON.toJSONString(</span>1.1<span style="color: #000000;">));
}

</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span><span style="color: #000000;"> String NJsonObjectToStringCompare(Group group) {
    String jsonString </span>=<span style="color: #000000;"> JSON.toJSONString(group);
    System.out.println(</span>"---------- 非JsonObject toString() toJSONString() 比较: ----------"<span style="color: #000000;">);
    System.out.println(group.toString());
    System.out.println(JSON.toJSONString(group));
    </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> jsonString;
}

</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span><span style="color: #000000;"> String JsonObjectToStringCompare(String ss) {
    Object o</span>=<span style="color: #000000;">JSON.parse(ss,Feature.OrderedField);
    System.out.println(</span>"---------- JsonObject toString() toJSONString() 比较: ----------"<span style="color: #000000;">);
    System.out.println(o.toString());
    System.out.println(JSON.toJSONString(o));
    </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> ss;
}



</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> JsonStringSequence(Group group, String jsonString) {
    System.out.println(</span>"---------- 是否有序: ----------"<span style="color: #000000;">);
    Object o</span>=<span style="color: #000000;">JSON.parse(jsonString);
    System.out.println(o.toString());;
    
    Object o1</span>=<span style="color: #000000;">JSON.parse(jsonString,Feature.OrderedField);
    System.out.println(o1.toString());
    
    Object o2 </span>=<span style="color: #000000;"> JSON.toJSON(group);
    System.out.println(o2.toString());
}

</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> JsonEval(String ss,String jsonPath) {
    System.out.println(</span>"---------- Json Eval: ----------"<span style="color: #000000;">);        
    Object o3</span>=<span style="color: #000000;">JSONPath.eval(JSON.parse(ss,Feature.OrderedField),jsonPath);
    System.out.println(o3.toString());
}

</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> DealWithNullToStringString(Group groupWithNull) {
    System.out.println(</span>"---------- JsonObject with null emlement: ----------"<span style="color: #000000;">);
    System.out.println(JSON.toJSONString(groupWithNull));
    System.out.println(JSON.toJSONString(groupWithNull,SerializerFeature.WriteMapNullValue));
}

</span><span style="color: #0000ff;">private</span> <span style="color: #0000ff;">static</span><span style="color: #000000;"> Group GenerateGroup() {
    Group group </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> Group();
    group.setId(</span>1.1<span style="color: #000000;">);
    group.setName(</span>"admin"<span style="color: #000000;">);

    User guestUser </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> User();
    guestUser.setId(</span>2.2<span style="color: #000000;">);
    guestUser.setName(</span>"guest"<span style="color: #000000;">);

    User rootUser </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> User();
    rootUser.setId(</span>3.3<span style="color: #000000;">);
    rootUser.setName(</span>"root"<span style="color: #000000;">);

    group.addUser(guestUser);
    group.addUser(rootUser);
    </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> group;
}

</span><span style="color: #0000ff;">private</span> <span style="color: #0000ff;">static</span><span style="color: #000000;"> Group GenerateGroupWithNull() {
    Group group </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> Group();
    group.setId(</span>1.1<span style="color: #000000;">);
    group.setName(</span>""<span style="color: #000000;">);

    User guestUser1 </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> User();
    guestUser1.setId(</span><span style="color: #0000ff;">null</span><span style="color: #000000;">);
    guestUser1.setName(</span>"guest"<span style="color: #000000;">);

    User guestUser2 </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> User();
    guestUser2.setId(</span>3.3<span style="color: #000000;">);
    
    User guestUser3 </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> User();        

    group.addUser(guestUser1);
    group.addUser(guestUser2);
    group.addUser(guestUser3);
    </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> group;
}

}

结果：

---------- 基元类型 toString() toJSONString() 比较: ----------
ZifuChuan
"ZifuChuan"
true
true
1.1
1.1
---------- JsonObject toString() toJSONString() 比较: ----------
{"id":1.1,"name":"admin","users":[{"id":2.2,"name":"guest"},{"id":3.3,"name":"root"}]}
{"id":1.1,"name":"admin","users":[{"id":2.2,"name":"guest"},{"id":3.3,"name":"root"}]}
---------- 非JsonObject toString() toJSONString() 比较: ----------
Demo.Sample1.Group@23ab930d
{"id":1.1,"name":"admin","users":[{"id":2.2,"name":"guest"},{"id":3.3,"name":"root"}]}
---------- 是否有序: ----------
{"name":"admin","id":1.1,"users":[{"name":"guest","id":2.2},{"name":"root","id":3.3}]}
{"id":1.1,"name":"admin","users":[{"id":2.2,"name":"guest"},{"id":3.3,"name":"root"}]}
{"name":"admin","id":1.1,"users":[{"name":"guest","id":2.2},{"name":"root","id":3.3}]}
---------- Json Eval: ----------
[{"id":2.2,"name":"guest"},{"id":3.3,"name":"root"}]
---------- JsonObject with null emlement: ----------
{"id":1.1,"name":"","users":[{"name":"guest"},{"id":3.3},{}]}
{"id":1.1,"name":"","users":[{"id":null,"name":"guest"},{"id":3.3,"name":null},{"id":null,"name":null}]}

参考：

[1] Introducing JSON

[2] FastJson 教程