G s o n   c a n   n o t   d e serialize {"b":"abc"} into an instance of B since the class B is an inner class. if it was defined as static class B then Gson would have been able to deserialize the string. Another solution is to write a custom instance creator for B.

Java代码 

public class InstanceCreatorForB implements InstanceCreator<A.B> {  

  private final A a;  

  public InstanceCreatorForB(A a)  {  

    this.a = a;  

  }  

  public A.B createInstance(Type type) {  

    return a.new B();  

  }  

}  

The above is possible, but not recommended.

数组例子:

Java代码 

Gson gson = new Gson();  

int[] ints = {1, 2, 3, 4, 5};  

String[] strings = {"abc", "def", "ghi"};  

(Serialization)  

gson.toJson(ints);     ==> prints [1,2,3,4,5]  

gson.toJson(strings);  ==> prints ["abc", "def", "ghi"]  

(Deserialization)  

int[] ints2 = gson.fromJson("[1,2,3,4,5]", int[].class);  

==> ints2 will be same as ints  

 We also support multi-dimensional arrays, with arbitrarily complex element types

综合实例1:

Java代码 

public class ExampleBean {  

    private String  name;  

    private String  id;  

    private int    age;  

    private boolean isOk;  

    public ExampleBean(String name, String id, int age, boolean isOk) {  

        super();  

        this.name = name;  

        this.id = id;  

        this.age = age;  

        this.isOk = isOk;  

    }  

    public ExampleBean() {  

    }  

//setter和getter方法  

}  

 测试:

Java代码 

public static void main(String[] args) {  

        Gson gson = new Gson();  

        List<ExampleBean> list = new ArrayList<ExampleBean>();  

        for (int i = 0; i < 5; i++) {  

            String name = "xxlong" + i;  

            int age = 20 + i;  

            ExampleBean bean = new ExampleBean(name, i + "", age);  

            list.add(bean);  

        }  

        Type listType = new TypeToken<List<ExampleBean>>() {  

        }.getType();  

        //将list转化成json字符串  

        String json = gson.toJson(list);  

        System.out.println(json);  

        //将json字符串还原成list  

        List<ExampleBean> list2 = gson.fromJson(json, listType);  

    }  

 输出如下:[{"name":"xxlong0","id":"0","age":20,"isOk":false},{"name":"xxlong1","id":"1","age":21,"isOk":false},{"name":"xxlong2","id":"2","age":22,"isOk":false},{"name":"xxlong3","id":"3","age":23,"isOk":false},{"name":"xxlong4","id":"4","age":24,"isOk":false}]

综合实例2:

需求:想将字符串{'tableName' :'ys_index_y','year': '2008','params':'[z_expense,z_expense_profit,z_main_margin]','isOperAll':'false','copyToYear':''}还原成对象OpeerConditions,OpeerConditions对象代码如下所示:

Java代码 

public class OperConditions {  

    private String   tableName;  

    private String   year;  

    private String[]    params;  

    private boolean  isOperALl;  

    private String   copyToYear;  

    public OperConditions() {  

    }  

    public OperConditions(String tableName, String year, String[] params,  

                    boolean isOperALl, String copyToYear) {  

        super();  

        this.tableName = tableName;  

        this.year = year;  

        this.params = params;  

        this.setOperALl(isOperALl);  

        this.copyToYear = copyToYear;  

    }  

//getter和setter方法  

}  

 因为OperConditions中有属性params,它是一个数组,所以无论是用json lib还是gson都不能直接将上面的字符串还原成OperCondtions对象,可以直接将params分离出来，单独处理，我这里选用此种方法来处理：

json-lib代码如下：

Java代码 

public static void main(String[] args) {  

        String json = "{'tableName' :'ys_index_y','year': '2008','isOperAll':'false','copyToYear':''}";  

        JSONObject jsonObj = JSONObject.fromObject( json );   

        OperConditions conditions = (OperConditions) JSONObject.toBean( jsonObj, OperConditions.class );  

        System.out.println(conditions.isOperALl() == false); //==>输出为true  

        String json1 = "['z_expense','z_expense_profit','z_main_margin']";  

        JSONArray jsonArray = JSONArray.fromObject(json1);  

        //List<String> list = jsonArray.toList(jsonArray); //这个方法也可以  

        List<String> list = jsonArray.toList(jsonArray,String.class);  

        conditions.setParams(list.toArray(new String[0]));  

        System.out.println(conditions.getParams()[0]); //==>输出为z_expense  

    }  

 因为JSONArray的toArray()方法返回的是一个Object[]数组，所以先将它转化成list，再转化到String数组。

当然由JSONArray转化成list时也可以使用subList方法，如下所示：

Java代码 

List<String> list = jsonArray.subList(0, jsonArray.size());  

 或者可以直接使用JSONArray的iterator() 方法迭代它本身直接得到需要的String数组。

如果使用Gson来完成这一需求，个人感觉更简单，代码如下所示：

Java代码 

public static void main(String[] args) {  

        String json = "{'tableName' :'ys_index_y','year': '2008','isOperAll':'false','copyToYear':''}";  

        Gson gson = new Gson();  

        OperConditions conditions = gson.fromJson(json, OperConditions.class);  

        System.out.println(conditions.isOperALl() == false); // ==>输出为true  

        String json1 = "['z_expense','z_expense_profit','z_main_margin']";  

        String[] params = gson.fromJson(json1,String[].class);  

        conditions.setParams(params);  

        System.out.println(conditions.getParams()[0]); // ==>输出为z_expense  

    }  

 Gson可以直接转化成String[]数组，同时转化OperConditions时也比json-lib简单。