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因為gson網(wǎng)上的幫助文檔打開時比較慢,所以把幫助文檔摘錄如此,方便查看: 1. 基本類型轉(zhuǎn)化 Java代碼 public static void main(String[] args) { Gson gson = new Gson(); System.out.println(gson.toJson(1)); // ==> prints 1 System.out.println(gson.toJson("abcd"));// ==> prints "abcd" System.out.println(gson.toJson(new Long(10)));// ==> prints 10 int[] values = { 1 }; System.out.println(gson.toJson(values));// ==> prints [1] System.out.println("============"); int one = gson.fromJson("1", int.class); Integer one1 = gson.fromJson("1", Integer.class); Long one2 = gson.fromJson("1", Long.class); String str = gson.fromJson("\"abc\"", String.class); String anotherStr = gson.fromJson("[\"abc\"]", String.class); int[] ints = gson.fromJson("[1,2,3,4,5]", int[].class); Boolean b = gson.fromJson("false", Boolean.class); System.out.println(b == false); //==> prints true } 2.對象轉(zhuǎn)化 Java代碼 public class BagOfPrimitives { private int value1 = 1; private String value2 = "abc"; //是用于聲明變量在序列化的時候不被存儲 private transient int value3 = 3; BagOfPrimitives() { // no-args constructor } public static void main(String[] args) { BagOfPrimitives obj = new BagOfPrimitives(); Gson gson = new Gson(); String json = gson.toJson(obj); System.out.println(json); //==> json is {"value1":1,"value2":"abc"} BagOfPrimitives obj2 = gson.fromJson(json, BagOfPrimitives.class); System.out.println(obj2.value1); System.out.println(obj2.value2); System.out.println(obj2.value3);//==>3 String json1 = "{'value1':1,'value2':'abc','value3':4}"; BagOfPrimitives obj3 = gson.fromJson(json1, BagOfPrimitives.class); System.out.println(obj3.value1); System.out.println(obj3.value2); System.out.println(obj3.value3); //==>3 } } Note that you can not serialize objects with circular references since that will result in infinite recursion. 如果要是用json lib的話,上面的代碼可以寫成如下所示: Java代碼 String json1 = "{'value1':1,'value2':'abc','value3':4}"; JSONObject jsonObj = JSONObject.fromObject( json1 ); BagOfPrimitives obj3 = (BagOfPrimitives) JSONObject.toBean( jsonObj, BagOfPrimitives.class ); Finer Points with Objects It is perfectly fine (and recommended) to use private fields There is no need to use any annotations to indicate a field is to be included for serialization and deserialization. All fields in the current class (and from all super classes) are included by default. If a field is marked transient, (by default) it is ignored and not included in the JSON serialization or deserialization. This implementation handles nulls correctly While serialization, a null field is skipped from the output While deserialization, a missing entry in JSON results in setting the corresponding field in the object to null If a field is synthetic , it is ignored and not included in JSON serialization or deserialization Fields corresponding to the outer classes in inner classes, anonymous classes, and local classes are ignored and not included in serialization or deserialization Nested Classes (including Inner Classes) Gson can serialize static nested classes quite easily. Gson can also deserialize static nested classes. However, Gson can not automatically deserialize the pure inner classes since their no-args constructor also need a reference to the containing Object which is not available at the time of deserialization. You can address this problem by either making the inner class static or by providing a custom InstanceCreator for it. Here is an example: Java代碼 public class A { public String a; class B { public String b; public B() { // No args constructor for B } } } NOTE : The above class B can not (by default) be serialized with Gson. 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代碼 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. 數(shù)組例子: Java代碼 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 綜合實例1: Java代碼 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 } 測試: Java代碼 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(); //將list轉(zhuǎn)化成json字符串 String json = gson.toJson(list); System.out.println(json); //將json字符串還原成list List<ExampleBean> list2 = gson.fromJson(json, listType); } 輸出如下:[{"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}] 綜合實例2: 需求:想將字符串{'tableName' :'ys_index_y','year': '2008','params':'[z_expense,z_expense_profit,z_main_margin]','isOperAll':'false','copyToYear':''}還原成對象OpeerConditions,OpeerConditions對象代碼如下所示: Java代碼 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 } 因為OperConditions中有屬性params,它是一個數(shù)組,所以無論是用json lib還是gson都不能直接將上面的字符串還原成OperCondtions對象,可以直接將params分離出來，單獨處理，我這里選用此種方法來處理： json-lib代碼如下： Java代碼 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); //==>輸出為true String json1 = "['z_expense','z_expense_profit','z_main_margin']"; JSONArray jsonArray = JSONArray.fromObject(json1); //List<String> list = jsonArray.toList(jsonArray); //這個方法也可以 List<String> list = jsonArray.toList(jsonArray,String.class); conditions.setParams(list.toArray(new String[0])); System.out.println(conditions.getParams()[0]); //==>輸出為z_expense } 因為JSONArray的toArray()方法返回的是一個Object[]數(shù)組，所以先將它轉(zhuǎn)化成list，再轉(zhuǎn)化到String數(shù)組。 當然由JSONArray轉(zhuǎn)化成list時也可以使用subList方法，如下所示： Java代碼 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數(shù)組。 如果使用Gson來完成這一需求，個人感覺更簡單，代碼如下所示： Java代碼 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); // ==>輸出為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]); // ==>輸出為z_expense } Gson可以直接轉(zhuǎn)化成String[]數(shù)組，同時轉(zhuǎn)化OperConditions時也比json-lib簡單。 還有一點是非常值得注意的，就是你的bean中有boolean屬性值時，強烈建議你別像我這個例子中一樣命名為以is開頭的屬性名，這可能給你帶來意想不到的錯誤，關于這一點的詳細解說請參看我的文章json lib 學習筆記
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