Gson 转换树型结构的实例

构建树型结构的实体

树型结构的实体主要是用组合模式构建的，且是透明模式的组合模式；关于组合模式，此处不再赘述。

代码部分：

> package com.dp.composite.example4;

import com.google.gson.annotations.Expose;

import java.io.Serializable;
import java.util.ArrayList;

/**
* @desc 抽象的缺省类
* @creator caozhiqing
* @data 2015/8/12
*/
public abstract class Component implements Serializable{

private transient Component parent;

public Component getParent() {
return parent;
}

public void setParent(Component parent) {
this.parent = parent;
}

public void addChild(Component component){
throw new UnsupportedOperationException("不支持此方法");
}

public void getChild(int index) {
throw new UnsupportedOperationException("不支持此方法");
}

public ArrayList<Component> getChild() {
throw new UnsupportedOperationException("不支持此方法");
}

public void removeChile(Component component) {
throw new UnsupportedOperationException("不支持此方法");
}

public abstract void operation(String pre);
}

package com.dp.composite.example4;

import java.util.ArrayList;
import java.util.Iterator;

/**
* @desc 具体树枝类，即容器类
* @creator caozhiqing
* @data 2015/8/12
*/
public class Composite extends Component {

ArrayList<Component> children ;

private String name;
public Composite(String name){
this.name= name;
}

@Override
public void addChild(Component component) {
if(component == null){
return;
}
if(children == null){
children = new ArrayList<Component>();
}
children.add(component);
component.setParent(this);
}

@Override
public void removeChile(Component component) {
if(component == null || children == null){
return;
}
Iterator<Component> iterator = children.iterator();
while (iterator.hasNext()){
Component component1 = iterator.next();
if(component1 != null && component1 == component){
iterator.remove();
if(component instanceof Composite && component1.getChild() != null){
for(Component component2:component.getChild()){
component2.setParent(this);
addChild(component2);
}
}
break;
}
}
}

@Override
public ArrayList<Component> getChild() {
return children;
}

@Override
public void operation(String pre) {
System.out.println(pre+"#"+this.name);
pre +="   ";
if(children != null && children.size()>0){
for(Component component:children){
component.operation(pre);
}
}
}
}

package com.dp.composite.example4;

/**
* @desc 叶子类，即没有子节点
* @creator caozhiqing
* @data 2015/8/12
*/
public class Leaf extends Component {

private String name;
public Leaf(String name){
this.name = name;
}

@Override
public void operation(String pre) {

System.out.println(pre+"-"+this.name);
}
}

package com.dp.composite.example4;

import com
4000
.google.gson.Gson;

/**

* @desc 客户端

* @creator caozhiqing

* @data 2015/8/12

*/

public class Client {

public static void main(String[] arg){

Component root = new Composite(“服装”);

Component man = new Composite(“男装”);

Component wom = new Composite(“女装”);

root.addChild(man);
root.addChild(wom);

Component leaf1 = new Leaf("夹克");
Component leaf2 = new Leaf("寸衫");
man.addChild(leaf1);
man.addChild(leaf2);

Component leaf3 = new Leaf("短裙");
Component leaf4 = new Leaf("Browse");
wom.addChild(leaf3);
wom.addChild(leaf4);
root.operation("");

System.out.println("----------->");

// root.removeChile(man);

// root.operation(“”);

Gson gson = new Gson();

System.out.println(gson.toJson(root));

}

}

“`

解析

此处最主要的是忽略每个子节点的父节点。



即在Component 中把此属性设置为transient 即不被序列化，且不能使用Gson提供的@Expose(serialize = false) 或@Expose（与new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create() ）配合使用。

JSON 结果。

{“children”:[{“children”:[{“name”:”夹克”},{“name”:”寸衫”}],”name”:”男装”},{“children”:[{“name”:”短裙”},{“name”:”Browse”}],”name”:”女装”}],”name”:”服装”}

- 总结：

如果古加入transient关键字，会报栈溢出的bug

这回crm系统封装解析json和以树型为结构的json解析很有帮助。