Json数据的解析_Gson

一些简单的JSON格式解析可以直接使用JSONObject和JSONArray来解析，但是面对比较复杂或者是数据量较大的JSON数据时就需要使用fastJSON和Gson来解析了，这样的效率和效果都更好

这里介绍本次项目使用到的Gson解析，fastJSON类似，但是由于如果包含了fastJSON,那么在proguard混淆的时候需要在rule中包含以下内容：

-keepattributes Signature     // 避免混淆泛型
-keepattributes *Annotation*　//　不混淆注解

如果不包含的话，就会出现以下几个问题：
１.　加了符号Annotation的实体属性后，一使用就崩溃
２. 当有泛型属性时，一使用就崩溃

接下来就先总结一下Gson的解析

GSON 简单解析

先是解析JSONObject

Gson gson = new Gson();
Person person = gson.fromJson(response, Person.class);

再是解析JSONArray
需要借助TypeToken将期望解析成的数据类型传入fromJson方法

Gson gson = new Gson();
List datas = gson.fromJson(response, new TypeToken<List>(){}.getType());

GSON 复杂解析

JSON返回的数据如下：

{"code":0,"desc":"Success","content":{"grade":14,"signin":false,"room":"","docs":[{"id":331,"docname":"[SFTM财务系统改善]成本支付-2.xlsxsdfsdfsdfsdfsdfsdfsdfsdfsdfsdfsd.xlsx","pagecnt":8,"doctime":"2015-11-28"},{"id":332,"docname":"外勤1.0需求细分列表修改版.docx","pagecnt":4,"doctime":"2015-11-28"},{"id":333,"docname":"1.docx","pagecnt":1,"doctime":"2015-11-29"},{"id":334,"docname":"要件签字封面（部品单价）.xls","pagecnt":3,"doctime":"2015-11-29"}],"printer":[{"id":1,"address":"5104"}]}}

上面的JSON数据总结一下，也就包含以下几个内容：
首先第一层是code, desc,content
第二层content中包含以下的内容：grade, signin, room, docs，printer
第三层docs中包含以下内容: id, docname, pagecnt, doctime
第三层printer中包含以下内容:id, address

对于这种比较复杂的JSON数据格式的解析，可以分成以下几步来做：

• 创建一个实体
• 在实体中包含３个属性
• 创建一个静态内部类，该类中包含的属性就是content中存在的内容，也就是grade, signin, room, docs，printer。如果content是一个[]，就应该定义为List,如果是{},就定义为DocContent
• 再在content创建的静态内部类中创建两个静态内部类：Docs和Printer

总体的效果如下：
第一层

 private int code;
 private String desc;
 private DocContent content;

第二层

public static class DocContent {
     private int grade;
     private Boolean signin;
     private String room;
     private List docs;
     private List printer;
}

第三层

public static class Docs {
    private String docname;
    private int pagecnt;
    private String doctime;
}

public static class Printer {
    private int id;
    private String address;
}

当然咯，其中还要包括各种setter和getter方法，只需要注意一点，这里的属性被声明为List是因为这个是一个JSONArray，对于JSONObject只需要直接定义

完整代码如下：

public class JsonDatas_DocInfo {

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }

    public DocContent getContent() {
        return content;
    }

    public void setContent(DocContent content) {
        this.content = content;
    }

    private int code;
    private String desc;
    private DocContent content;

    public static class DocContent {
        public int getGrade() {
            return grade;
        }

        public void setGrade(int grade) {
            this.grade = grade;
        }

        public Boolean getSignin() {
            return signin;
        }

        public void setSignin(Boolean signin) {
            this.signin = signin;
        }

        public String getRoom() {
            return room;
        }

        public void setRoom(String room) {
            this.room = room;
        }

        public List getDocs() {
            return docs;
        }

        public void setDocs(List docs) {
            this.docs = docs;
        }

        public List getPrinter() {
            return printer;
        }

        public void setPrinter(List printer) {
            this.printer = printer;
        }

        private int grade;
        private Boolean signin;
        private String room;
        private List docs;
        private List printer;

        public static class Docs {
            private int id;

            public int getId() {
                return id;
            }

            public void setId(int id) {
                this.id = id;
            }

            public String getDocname() {
                return docname;
            }

            public void setDocname(String docname) {
                this.docname = docname;
            }

            public int getPagecnt() {
                return pagecnt;
            }

            public void setPagecnt(int pagecnt) {
                this.pagecnt = pagecnt;
            }

            public String getDoctime() {
                return doctime;
            }

            public void setDoctime(String doctime) {
                this.doctime = doctime;
            }

            private String docname;
            private int pagecnt;
            private String doctime;
        }

        public static class Printer {
            public int getId() {
                return id;
            }

            public void setId(int id) {
                this.id = id;
            }

            public String getAddress() {
                return address;
            }

            public void setAddress(String address) {
                this.address = address;
            }

            private int id;
            private String address;
        }
    }
}

调用的方法：

                Gson gson = new Gson();
                JsonDatas_DocInfo jsonDatas_docInfo = gson.fromJson(response, JsonDatas_DocInfo.class);
                List.DocContent.Docs> docs = jsonDatas_docInfo.getContent().getDocs();

                if (docs != null) {
                    for (JsonDatas_DocInfo.DocContent.Docs tempDoc : docs) {
                        final int id = tempDoc.getId();
                        final String docname = tempDoc.getDocname();
                        final int pagecnt = tempDoc.getPagecnt();
                        final String doctime = tempDoc.getDoctime();

                        Log.d("info", id + ", docname:" + docname + ", pagecnt : " +
                                pagecnt + ", doctime : " + doctime);
                        listDocInfo.add(new DocInfo(id, docname, pagecnt, doctime));
                    }

                    handler.sendMessage(msg);
                }