如何保证spring bean中的线程安全

写在前面：这两天做了一个查询接口,由于查询条件和参数太多，采用了链式操作，链式操作的类是个spring  service 的bean，执行查询的过程中需要缓冲List HashMap 等线程不安全的对象，怎么办捏？
解决过程：
最终通过检索关键字“spring bean 线程安全”找到了答案：
http://www.cnblogs.com/doit8791/p/4093808.html
经过测试，ThreadLocal 是最高效的解决线程安全问题的方法，使用方法如下：

@Component
public class ProcessInstanceQueryImpl implements ProcessInstanceSampleQuery  {

/**
这种不是线程安全的对象不要放在service的成员变量中
private Map<String, Object> filtrations = new HashMap<String, Object>();
    private Map<String, JSONObject> boMap = new HashMap<String, JSONObject>();
    private Map<String, BpBasicInfo> basicInfoMap = new HashMap<String, BpBasicInfo>();
    private List<String> businessKeyList = new ArrayList<String>();**/
//创建一个ThreadLocal的类Single来缓冲那些每次查询链需要用到的成员变量
 private static ThreadLocal<Single> signal = new ThreadLocal<Single>();
 private static enum RelativeCode {
        RELATIVE, RELATIVED, MERGE, MERGED, SPLIT, SPLITED
    };

 @Resource
 private  UniversalManager universalManager;

//Single类用来缓冲那些每次查询链需要用到的成员变量
 private static class Single {
        private BpQuery<?, ?> query;
        private List<String> boQuerys;

        private String boFilterHql;
        private String bpInfoHql;
        private StringBuilder boHql;
        private String orderHql;
        private String sortType;
        private String queryType;

        private Single() {
            boQuerys = new ArrayList<String>();
            boFilterHql = "select new com.cayenne.bpm.workbench.model.BpBasicInfoAndBo(bpInfo1,bo) from ${boName} as bo ,BpBasicInfo as bpInfo1 where bo.id=bpInfo1.boId ";
            bpInfoHql = "and bo.id in(select bpInfo.boId  from BpBasicInfo as bpInfo where 1=1";
            orderHql = "";
            sortType = "";
            queryType = "";
            boHql = new StringBuilder(" ");
        }

    }
//每次调用该service进行链式查询时，先初始化查询链，创建一个Single线程安全对象
    @Override
    public ProcessInstanceSampleQuery initProcessInstanceSampleQuery() { 
        //set线程安全的查询对象
        signal.set(new Single());
        return this;
    }
    @Override
    public ProcessInstanceSampleQuery queryTask(String processDefinitionKey) {
        //获取线程安全对象，并赋值
        signal.get().query = createCandiatesQuery(processDefinitionKey);
    }

结论：
需要在同一个线程中调用的对象，
定义时，ThreadLocal<Single> signal = new ThreadLocal<Single>();
初始化时，signal.set(new Single());
获取时,signal.get();（在未调用set方法之前，都是同一个线程之前set的signal值）
如果想要每次signal.get();获取的是初始化后的结果，那么定义时写成：ThreadLocal<Single> signal = new ThreadLocal<Single>(){
  @Override
        protected Single initialValue() {
            return new Single();
        }
};