Android客户端与服务器端的json数据交互（内含大量知识点）

服务器端数据库用的是 oracle 下面是建表语句 CREATE TABLE "HSX"."USERMSG" ( "USERNAME" VARCHAR2(20 BYTE) NOT NULL ENABLE, "PASSWORD" VARCHAR2(20 BYTE) NOT NULL ENABLE, "SEX" VARCHAR2(20 BYTE) NOT NULL ENABLE, "AGE" VARCHAR2(20 BYTE) NOT NULL ENABLE, "PHOTO" VARCHAR2(1000 BYTE) NOT NULL ENABLE, CONSTRAINT "USERMSG_PK" PRIMARY KEY ("USERNAME") USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT) TABLESPACE "USERS" ENABLE ) SEGMENT CREATION IMMEDIATE PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS LOGGING STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT) TABLESPACE "USERS" ;