这几天遇到个解析json的问题,返回的json数据中包含不同的实体类,实体类的键值是确定的但是类型是不确定的。(描述可能不对,下面给出json例子)
json数据例子如下:
String dataA = "{a:1, b:'Hello,world!', c:true, d:{aa:1}}";
String dataB = "{a:2, b:'Hello,world!', c:true, d:{ba:1, bb:'Hello word!'}}";
String dataC = "{a:3, b:'Hello,world!', c:true, d:{ca:1, cb:'Hello,:world!', cc:true}}";
网上找了很久,首先找到定义d为泛型,然后用JSONObject jsond = new JSONObject(String arg0)的方法得到d的json数据,最后用D d = gson.fromJson( jsond.toString(), D.class)解析出具体的实体类。下面看一下具体的实现。
Entity.java
public class Entity {
private int a;
private String b;
private boolean c;
private Object d;
public int getA() {
return a;
}
public void setA(int a) {
this.a = a;
}
public String getB() {
return b;
}
public void setB(String b) {
this.b = b;
}
public boolean isC() {
return c;
}
public void setC(boolean c) {
this.c = c;
}
public Object getD() {
return d;
}
public void setD(Object d) {
this.d = d;
}
@Override
public String toString() {
return "Entity [a=" + a + ", b=" + b + ", c=" + c + ", d=" + d + "]";
}
}
DA.javapublic class DA {
private int aa;
public int getAa() {
return aa;
}
public void setAa(int aa) {
this.aa = aa;
}
@Override
public String toString() {
return "DA [aa=" + aa + "]";
}
}
DB.java
public class DB {
private int ba;
private String bb;
public int getBa() {
return ba;
}
public void setBa(int ba) {
this.ba = ba;
}
public String getBb() {
return bb;
}
public void setBb(String bb) {
this.bb = bb;
}
@Override
public String toString() {
return "DB [ba=" + ba + ", bb=" + bb + "]";
}
}
DC.java
public class DC {
private int ca;
private String cb;
private boolean cc;
public DC(int ca, String cb, boolean cc) {
super();
this.ca = ca;
this.cb = cb;
this.cc = cc;
}
public int getCa() {
return ca;
}
public void setCa(int ca) {
this.ca = ca;
}
public String getCb() {
return cb;
}
public void setCb(String cb) {
this.cb = cb;
}
public boolean isCc() {
return cc;
}
public void setCc(boolean cc) {
this.cc = cc;
}
@Override
public String toString() {
return "DC [ca=" + ca + ", cb=" + cb + ", cc=" + cc + "]";
}
}
jsontest.javaimport com.google.gson.Gson;
import com.mathworks.toolbox.javabuilder.external.org.json.JSONObject;
public class jsontest {
public static void main(String[] args) {
String dataA = "{a:1, b:'Hello,world!', c:true, d:{aa:1}}";
String dataB = "{a:2, b:'Hello,world!', c:true, d:{ba:1, bb:'Hello word!'}}";
String dataC = "{a:3, b:'Hello,world!', c:true, d:{ca:1, cb:'Hello,:world!', cc:true}}";
Gson gson = new Gson();
Entity ea = gson.fromJson(dataA, Entity.class);
Entity eb = gson.fromJson(dataB, Entity.class);
Entity ec = gson.fromJson(dataC, Entity.class);
System.out.println("ea ="+ea.toString());
System.out.println("eb ="+eb.toString());
System.out.println("ec ="+ec.toString());
ea = gson.fromJson(dataA, Entity.class);
eb = gson.fromJson(dataB, Entity.class);
ec = gson.fromJson(dataC, Entity.class);
if(ea.getA()==1){
System.out.println("ea.getD() ="+ea.getD().toString());
try {
JSONObject d = new JSONObject(ea.getD().toString());
System.out.println("d ="+d.toString());
DA da = gson.fromJson(d.toString(), DA.class);
System.out.println("da ="+da.toString());
} catch (Exception e) {
e.printStackTrace();
}
}
System.out.println("");
if(eb.getA()==2){
System.out.println("eb.getD() ="+eb.getD().toString());
try {
JSONObject d = new JSONObject(eb.getD().toString());
System.out.println("d ="+d.toString());
DB db = gson.fromJson(d.toString(), DB.class);
System.out.println("db ="+db.toString());
} catch (Exception e) {
e.printStackTrace();
}
}
System.out.println("");
if(ec.getA()==3){
System.out.println("ec.getD() ="+ec.getD().toString());
try {
JSONObject d = new JSONObject(ec.getD().toString());
System.out.println("d ="+d.toString());
DC dc = gson.fromJson(d.toString(), DC.class);
System.out.println("dc ="+dc.toString());
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
运行结果:
ea =Entity [a=1, b=Hello,world!, c=true, d={aa=1.0}]
eb =Entity [a=2, b=Hello,world!, c=true, d={ba=1.0, bb=Hello word!}]
ec =Entity [a=3, b=Hello,world!, c=true, d={ca=1.0, cb=Hello,:world!, cc=true}]
ea.getD() ={aa=1.0}
d ={"aa":1}
da =DA [aa=1]
eb.getD() ={ba=1.0, bb=Hello word!}
d ={"bb":"Hello word!","ba":1}
db =DB [ba=1, bb=Hello word!]
ec.getD() ={ca=1.0, cb=Hello,:world!, cc=true}
com.mathworks.toolbox.javabuilder.external.org.json.JSONException: Missing value at character 18 of {ca=1.0, cb=Hello,:world!, cc=true}
at com.mathworks.toolbox.javabuilder.external.org.json.JSONTokener.syntaxError(JSONTokener.java:451)
at com.mathworks.toolbox.javabuilder.external.org.json.JSONTokener.nextValue(JSONTokener.java:349)
at com.mathworks.toolbox.javabuilder.external.org.json.JSONObject.<init>(JSONObject.java:191)
at com.mathworks.toolbox.javabuilder.external.org.json.JSONObject.<init>(JSONObject.java:327)
at com.example.json.jsontest.main(jsontest.java:51)
当dataC = "{a:3, b:'Hello,world!', c:true, d:{ca:1, cb:'Hello,world!', cc:true}}";
报错
com.mathworks.toolbox.javabuilder.external.org.json.JSONException: Expected a ':' after a key at character 25 of {ca=1.0, cb=Hello,world!, cc=true}at com.mathworks.toolbox.javabuilder.external.org.json.JSONTokener.syntaxError(JSONTokener.java:451)at
com.mathworks.toolbox.javabuilder.external.org.json.JSONObject.<init>(JSONObject.java:204)at com.mathworks.toolbox.javabuilder.external.org.json.JSONObject.<init>(JSONObject.java:327)at com.example.json.jsontest.main(jsontest.java:51)
当dataC = "{a:3, b:'Hello,world!', c:true, d:{ca:1, cb:'Hello:world!', cc:true}}";
报错
com.mathworks.toolbox.javabuilder.external.org.json.JSONException: Expected a ',' or '}' at character 18 of {ca=1.0, cb=Hello:world!, cc=true}
at com.mathworks.toolbox.javabuilder.external.org.json.JSONTokener.syntaxError(JSONTokener.java:451)
at com.mathworks.toolbox.javabuilder.external.org.json.JSONObject.<init>(JSONObject.java:223)
at com.mathworks.toolbox.javabuilder.external.org.json.JSONObject.<init>(JSONObject.java:327)
at com.example.json.jsontest.main(jsontest.java:51)
当dataC = "{a:3, b:'Hello,world!', c:true, d:{ca:1, cb:'Hello,:world!', cc:true}}";
报错
com.mathworks.toolbox.javabuilder.external.org.json.JSONException: Missing value at character 18 of {ca=1.0, cb=Hello,:world!, cc=true}
at com.mathworks.toolbox.javabuilder.external.org.json.JSONTokener.syntaxError(JSONTokener.java:451)
at com.mathworks.toolbox.javabuilder.external.org.json.JSONTokener.nextValue(JSONTokener.java:349)
at com.mathworks.toolbox.javabuilder.external.org.json.JSONObject.<init>(JSONObject.java:191)
at com.mathworks.toolbox.javabuilder.external.org.json.JSONObject.<init>(JSONObject.java:327)
at com.example.json.jsontest.main(jsontest.java:51)
如果收到的json数据是dataC = "{a:3, b:'Hello,world!', c:true, d:{ca:1, cb:\'\"Hello,world!\"\', cc:true}}";则可以解析,因为第一次解析得到的是{ca=1.0, cb="Hello,world!", cc=true},可以转换成json数据,但是别人不可能按我的需求这样发给我。
然后在网上继续找字符串转换为实体类,发现很多人说啥反射工厂模式,觉得意思就和编译原理里的词法分析、语法分析差不多,就是一个一个地进行匹配,然后我就像下面这样做。
jsonsubtest.java
import com.google.gson.Gson;
public class jsonsubtest {
public static void main(String[] args) {
String dataA = "{a:1, b:'Hello,world!', c:true, d:{aa:1}}";
String dataB = "{a:2, b:'Hello,world!', c:true, d:{ba:1, bb:'Hello word!'}}";
String dataC = "{a:3, b:'Hello,world!', c:true, d:{ca:1, cb:'Hello,world!', cc:true}}";
Gson gson = new Gson();
DC dctest = new DC(1, null, false);
String jsondctest = gson.toJson(dctest, DC.class);
System.out.println("jsondctest ="+jsondctest);
Entity ea = gson.fromJson(dataA, Entity.class);
Entity eb = gson.fromJson(dataB, Entity.class);
Entity ec = gson.fromJson(dataC, Entity.class);
System.out.println("ea ="+ea.toString());
System.out.println("eb ="+eb.toString());
System.out.println("ec ="+ec.toString());
DC dc1 = getD(ec.getD().toString());
System.out.println("dc1 ="+dc1.toString());
DC dc2 = getD("{ca=1.0, cc=true}");
System.out.println("dc2 ="+dc2.toString());
DC dc3 = getD("{ca=1.0, cb=Hello,cc=world!, cc=true}");
System.out.println("dc3 ="+dc3.toString());
DC dc4 = getDcut("{ca=1.0, cb=Hello,cc=world!, cc=true}");
System.out.println("dc4 ="+dc4.toString());
DC dc5 = getDcut("{ca=1.0, cb=Hello, cc=world!, cc=true}");
System.out.println("dc5 ="+dc5.toString());
}
public static DC getD(String srcstr) {//{ca=1.0, cb=Hello,world!, cc=true} {ca=1.0, cc=true}
int a = 0;
String b = null;
boolean c = false;
String temp = "";
int start,end = 0;
start = srcstr.indexOf("ca=");
if(start!=-1){
temp = srcstr.substring(start);
end = temp.indexOf(", ");
if(end!=-1)
a = (int) Float.parseFloat(temp.substring(3, end));
}
start = srcstr.indexOf("cb=");
if(start!=-1){
temp = srcstr.substring(start);
end = temp.indexOf(", cc");
if(end!=-1)
b = temp.substring(3, end);
}
start = srcstr.indexOf("cc=");
if(start!=-1){
temp = srcstr.substring(start);
end = temp.indexOf("}");
if(end!=-1)
c = Boolean.parseBoolean(temp.substring(3, end));
}
DC dc = new DC(a, b, c);
return dc;
}
private static DC getDcut(String srcstr) {
int a = 0;
String b = null;
boolean c = false;
String temp = "";
int start,end = 0;
System.out.println("srcstr1 ="+srcstr);
start = srcstr.indexOf("ca=");
if(start!=-1){
temp = srcstr.substring(start);
end = temp.indexOf(", ");
if(end!=-1)
a = (int) Float.parseFloat(temp.substring(3, end));
}
if(start!=-1 && end!=-1){
temp = srcstr.substring(start, end+2);
srcstr = srcstr.replace(temp, "");
}
System.out.println("srcstr2 ="+srcstr);
start = srcstr.indexOf("cb=");
if(start!=-1){
temp = srcstr.substring(start);
end = temp.indexOf(", cc");
if(end!=-1)
b = temp.substring(3, end);
}
if(start!=-1 && end!=-1){
temp = srcstr.substring(start, end+4);
srcstr = srcstr.replace(temp, "");
}
System.out.println("srcstr3 ="+srcstr);
start = srcstr.indexOf("cc=");
if(start!=-1){
temp = srcstr.substring(start);
end = temp.indexOf("}");
if(end!=-1)
c = Boolean.parseBoolean(temp.substring(3, end));
}
DC dc = new DC(a, b, c);
return dc;
}
}
运行结果:
jsondctest ={"ca":1,"cc":false}
ea =Entity [a=1, b=Hello,world!, c=true, d={aa=1.0}]
eb =Entity [a=2, b=Hello,world!, c=true, d={ba=1.0, bb=Hello word!}]
ec =Entity [a=3, b=Hello,world!, c=true, d={ca=1.0, cb=Hello,world!, cc=true}]
dc1 =DC [ca=1, cb=Hello,world!, cc=true]
dc2 =DC [ca=1, cb=null, cc=true]
dc3 =DC [ca=1, cb=Hello,cc=world!, cc=false]
srcstr1 ={ca=1.0, cb=Hello,cc=world!, cc=true}
srcstr2 ={ cb=Hello,cc=world!, cc=true}
srcstr3 ={ cc=true}
dc4 =DC [ca=1, cb=Hello,cc=world!, cc=true]
srcstr1 ={ca=1.0, cb=Hello, cc=world!, cc=true}
srcstr2 ={ cb=Hello, cc=world!, cc=true}
srcstr3 ={ cc=world!, cc=true}
dc5 =DC [ca=1, cb=Hello, cc=false]

后来在http://blog.youkuaiyun.com/yuanguozhengjust/article/details/50477128才发现可以这样做。
EntityT.java
public class EntityT <T>{
private int a;
private String b;
private boolean c;
private T d;
public int getA() {
return a;
}
public void setA(int a) {
this.a = a;
}
public String getB() {
return b;
}
public void setB(String b) {
this.b = b;
}
public boolean isC() {
return c;
}
public void setC(boolean c) {
this.c = c;
}
public T getD() {
return d;
}
public void setD(T d) {
this.d = d;
}
@Override
public String toString() {
return "EntityT [a=" + a + ", b=" + b + ", c=" + c + ", d=" + d + "]";
}
}
jsonentitytest.java
import java.lang.reflect.Type;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
public class jsonentitytest {
public static void main(String[] args) {
String dataA = "{a:1, b:'Hello,world!', c:true, d:{aa:1}}";
String dataB = "{a:2, b:'Hello,world!', c:true, d:{ba:1, bb:'Hello word!'}}";
String dataC = "{a:3, b:'Hello,world!', c:true, d:{ca:1, cb:'Hello,world!', cc:true}}";
// String dataA = "{a:1, b:'Hello,world!', c:true, d:{aa:1}}";
// String dataB = "{a:2, b:'Hello,world!', c:true, d:{ba:1, bb:\'\"Hello,word!\"\'}}";
// String dataC = "{a:3, b:'Hello,world!', c:true, d:{ca:1, cb:\'\"Hello,world!\"\', cc:true}}";
// String dataA = "{\"a\":1, \"b\":\"Hello,world!\", \"c\":true, \"d\":{\"aa\":1}}";
// String dataB = "{\"a\":2, \"b\":\"Hello,world!\", \"c\":true, \"d\":{\"ba\":1, \"bb\":\'\"Hello,world!\"\'}}";
// String dataC = "{\"a\":3, \"b\":\"Hello,world!\", \"c\":true, \"d\":{\"ca\":1, \"cb\":\'Hello,world!\', \"cc\":true}}";
Gson gson = new Gson();
DC dctest = new DC(1, null, false);
String jsondctest = gson.toJson(dctest, DC.class);
System.out.println("jsondctest ="+jsondctest);
EntityT ea = gson.fromJson(dataA, EntityT.class);
EntityT eb = gson.fromJson(dataB, EntityT.class);
EntityT ec = gson.fromJson(dataC, EntityT.class);
System.out.println("ea ="+ea.toString());
System.out.println("eb ="+eb.toString());
System.out.println("ec ="+ec.toString());
System.out.println("");
if(ea.getA()==1){
Type jsonType = new TypeToken<EntityT<DA>>() {}.getType();
ea = gson.fromJson(dataA, jsonType);
System.out.println("ea ="+ea.toString());
}
if(eb.getA()==2){
Type jsonType = new TypeToken<EntityT<DB>>() {}.getType();
eb = gson.fromJson(dataB, jsonType);
System.out.println("eb ="+eb.toString());
}
if(ec.getA()==3){
Type jsonType = new TypeToken<EntityT<DC>>() {}.getType();
ec = gson.fromJson(dataC, jsonType);
System.out.println("ec ="+ec.toString());
}
}
}
至此已经能满足我的需求了,也没精神再找新方法了,睡觉
本文链接http://blog.youkuaiyun.com/qq_25189723/article/details/78848521