9、解析复杂Json

场景一

没有头的Json数组
“e:/person”文件内容如下，文件中是没有头的json数组

[
    {
        "id" : 1,
        "name" : "lzj",
        "age" : 27
    },
    {
        "id" : 2,
        "name" : "Bob",
        "age" : 20
    },
    {
        "id" : 3,
        "name" : "Terry",
        "age" : 26
    }
]

    /*也可用JsonReader来实现*/
    @Test
    public void test1() throws FileNotFoundException{
        GsonBuilder builder = new GsonBuilder();
        Gson gson = builder.create();
        FileReader fileReader = new FileReader("e:/person");
        JsonParser parser = new JsonParser();
        JsonElement jsonElement = parser.parse(fileReader);
        JsonArray asJsonArray = jsonElement.getAsJsonArray();
        List<Person> persons = new ArrayList<Person>();
        /*JsonArray继承自JsonElement，JsonArray是JsonElement数组形式*/
        for(JsonElement elment : asJsonArray){
            Person person = gson.fromJson(elment, Person.class);
            persons.add(person);
        }
        System.out.println(persons);
    }

运行程序，输出如下：

[Person [id=1, name=lzj, age=27], Person [id=2, name=Bob, age=20], Person [id=3, name=Terry, age=26]]

场景二

有头的Json数组
“e:/person1”文件中json字符串内容如下：

{
    "persons" :[
        {
            "id" : 1,
            "name" : "lzj",
            "age" : 27
        },
        {
            "id" : 2,
            "name" : "Bob",
            "age" : 20
        },
        {
            "id" : 3,
            "name" : "Terry",
            "age" : 26
        }
    ]

}

    @Test
    public void test2() throws FileNotFoundException{
        GsonBuilder builder = new GsonBuilder();
        Gson gson = builder.create();
        FileReader fileReader = new FileReader("e:/person1");
        JsonParser parser = new JsonParser();
        JsonElement jsonElement = parser.parse(fileReader);
        JsonObject jsonObject = jsonElement.getAsJsonObject();
        JsonArray jsonArray = jsonObject.getAsJsonArray("persons");
        List<Person> persons = new ArrayList<Person>();
        for(JsonElement elment : jsonArray){
            Person person = gson.fromJson(elment, Person.class);
            persons.add(person);
        }
        System.out.println(persons);
    }

运行程序，输出如下

[Person [id=1, name=lzj, age=27], Person [id=2, name=Bob, age=20], Person [id=3, name=Terry, age=26]]

场景三

Json数组外含有其他Json字符串
“e:/person2”文件中字符串如下

{
    "code" : 200,
    "persons" :[
        {
            "id" : 1,
            "name" : "lzj",
            "age" : 27
        },
        {
            "id" : 2,
            "name" : "Bob",
            "age" : 20
        },
        {
            "id" : 3,
            "name" : "Terry",
            "age" : 26
        }
    ]

}

    @Test
    public void test3() throws FileNotFoundException{
        GsonBuilder builder = new GsonBuilder();
        Gson gson = builder.create();
        FileReader fileReader = new FileReader("e:/person2");
        Persons persons = gson.fromJson(fileReader, Persons.class);
        System.out.println(persons.getPersons());
    }

运行程序，输出内容如下：

[Person [id=1, name=lzj, age=27], Person [id=2, name=Bob, age=20], Person [id=3, name=Terry, age=26]]

也可以用上一示例的方法进行解决，只是去获取“persons”中的内容就可以了。场景二中的代码只需要把读取的文件修改为“e:/person2”,拿过来可以直接使用。