Json传递后台数据的问题

在后台我有两个类：

    public Class Person {
    private String name;
    private Address address;//一个自定义的类
    //getter和setter方法省略
    }  

    public Class Address {
    private String road;
    //getter和setter方法省略
    }  

逻辑类：

    @Controller
    public class PersonController {  

        @Autowired
        private PersonService personService;  

        @RequestMapping(value = "getPersons.htm", method = RequestMethod.GET)
        public ModelAndView view() {
            System.out.println("success");
            List<Person> persons = personService.getPersons();//自定义的方法
            Map<String, Object> modelMap = new HashMap<String, Object>();
            modelMap.put("persons", persons);
            return new ModelAndView(modelMap);
        }
    }  

在js看到获取到的json数据是这样的：

    {"persons":[{"address":{"road":"商业街"},"name":"小明"},{"address":{"road":"莲花街"},"name":"小红"}]}  

前台代码：

    Ext.onReady(function() {  

                var store = new Ext.data.Store({
                            proxy : new Ext.data.HttpProxy({
                                        url : 'getPersons.htm'
                                    }),
                            reader : new Ext.data.JsonReader({
                                        root : 'books'
                                    }, [{
                                                name : 'name'
                                            }, {
                                                name : 'address'
                                            }])
                        });  

                var persons = new Ext.grid.GridPanel({
                            store : store,
                            cm : new Ext.grid.ColumnModel({
                                        defaults : {
                                            sortable : true,
                                            width :
                                        },
                                        columns : [{
                                                    header : "name",
                                                    dataIndex : 'name'
                                                }, {
                                                    header : "address",
                                                    dataIndex : 'address'
                                                }]
                                    }),
                            width : ,
                            height : ,
                            title : 'Test',
                            renderTo : 'persons'
                        });  

                store.load();
            });  

    var str = '[{"persons":[{"address":{"road":"商业街"},"name":"小明"},{"address":{"road":"莲花街"},"name":"小红"}]}]';
                  str = eval(str);
                  for(var i=;i<str.length;i++){
                    var strpersons= str[i].persons;
                    for(var j=;j<strpersons.length;j++){
                        alert(strpersons[j].name);
                        alert(strpersons[j].address.road);
                    }
                  }