开始再看这个crud示例时，居然发现我没有准备数据库信息及数据也可以运行成功，后来看了实现才明白，该示例使用了Map模拟数据库存储操作数据，不过struts2的实现还是又可以观飨的地方，下面就看看它的实现。
首先，定义持久类存储接口Storage：
public interface Storage extends Serializable {
IdEntity get( Class entityClass, Serializable id );
Serializable create ( IdEntity object ) throws CreateException;
IdEntity update ( IdEntity object ) throws UpdateException;
Serializable merge ( IdEntity object ) throws StorageException;
int delete( Class entityClass, Serializable id ) throws CreateException;
int delete( IdEntity object ) throws CreateException;
Collection findAll( Class entityClass );
}
很明了，定义了操作数据的几种的方法，然后实现了一种使用map存储数据的方式（当然你可以使用自己存储数据的方式实现，比如xml等等）代码如下：
public class MemoryStorage implements Storage {
private static final long serialVersionUID = 8611213748834904125L;
private Map memory = new HashMap();
private Map getEntityMap ( Class entityClass ) {
if (entityClass != null) {
Map tryMap = (Map) memory.get(entityClass);
if (tryMap == null) {
synchronized(memory) {
tryMap = new HashMap();
memory.put(entityClass, tryMap);
}
}
return tryMap;
} else {
return null;
}
}
private IdEntity intStore( Class entityClass, IdEntity object ) {
getEntityMap(entityClass).put(object.getId(), object);
return object;
}
public IdEntity get( Class entityClass, Serializable id ) {
if (entityClass != null && id != null) {
return (IdEntity) getEntityMap(entityClass).get(id);
} else {
return null;
}
}
public Serializable create ( IdEntity object ) throws CreateException {
if (object == null) {
throw new CreateException("Either given class or object was null");
}
if (object.getId() == null) {
throw new CreateException("Cannot store object with null id");
}
if (get(object.getClass(), object.getId()) != null) {
throw new DuplicateKeyException("Object with this id already exists.");
}
return intStore(object.getClass(), object).getId();
}
public IdEntity update ( IdEntity object ) throws UpdateException {
if (object == null) {
throw new UpdateException("Cannot update null object.");
}
if ( get(object.getClass(), object.getId())==null ) {
throw new UpdateException("Object to update not found.");
}
return intStore(object.getClass(), object);
}
public Serializable merge ( IdEntity object ) throws StorageException {
if (object == null) {
throw new StorageException("Cannot merge null object");
}
if (object.getId() == null || get(object.getClass(), object.getId())==null) {
return create(object);
} else {
return update(object).getId();
}
}
public int delete( Class entityClass, Serializable id ) throws CreateException {
try {
if (get(entityClass, id) != null) {
getEntityMap(entityClass).remove(id);
return 1;
} else {
return 0;
}
} catch (Exception e) {
throw new CreateException(e);
}
}
public int delete( IdEntity object ) throws CreateException {
if (object == null) {
throw new CreateException("Cannot delete null object");
}
return delete(object.getClass(), object.getId());
}
public Collection findAll( Class entityClass ) {
if (entityClass != null) {
return getEntityMap(entityClass).values();
} else {
return new ArrayList();
}
}
public void reset() {
this.memory = new HashMap();
}
}
其实就是map操作数据的几种方式（get，put...）
这样一种不使用数据库存储数据的方式就已经算完成了，不过我们需要初始几个数据怎么实现呢？struts2使用了spring的 InitializingBean 接口[Spirng的InitializingBean为bean提供了定义初始化方法的方式。InitializingBean是一个接口，它仅仅包含一个方法：afterPropertiesSet()。]代码如下：
public class TestDataProvider implements Serializable, InitializingBean {
private static final long serialVersionUID = 1L;
private static final Logger log = Logger.getLogger(TestDataProvider.class);
public static final String[] POSITIONS = {
"Developer",
"System Architect",
"Sales Manager",
"CEO"
};
public static final String[] LEVELS = {
"Junior",
"Senior",
"Master"
};
private static final Skill[] TEST_SKILLS = {
new Skill("WW-SEN", "Struts Senior Developer"),
new Skill("WW-JUN", "Struts Junior Developer"),
new Skill("SPRING-DEV", "Spring Developer")
};
public static final Employee[] TEST_EMPLOYEES = {
new Employee(new Long(1), "Alan", "Smithee", new Date(), new Float(2000f), true, POSITIONS[0],
TEST_SKILLS[0], null, "alan", LEVELS[0], "Nice guy"),
new Employee(new Long(2), "Robert", "Robson", new Date(), new Float(10000f), false, POSITIONS[1],
TEST_SKILLS[1], Arrays.asList(TEST_SKILLS).subList(1,TEST_SKILLS.length), "rob", LEVELS[1], "Smart guy")
};
private SkillDao skillDao;
private EmployeeDao employeeDao;
public void setSkillDao(SkillDao skillDao) {
this.skillDao = skillDao;
}
public void setEmployeeDao(EmployeeDao employeeDao) {
this.employeeDao = employeeDao;
}
protected void addTestSkills() {
try {
for (int i = 0, j = TEST_SKILLS.length; i < j; i++) {
skillDao.merge(TEST_SKILLS[i]);
}
if (log.isInfoEnabled()) {
log.info("TestDataProvider - [addTestSkills]: Added test skill data.");
}
} catch (StorageException e) {
log.error("TestDataProvider - [addTestSkills]: Exception catched: " + e.getMessage());
}
}
protected void addTestEmployees() {
try {
for (int i = 0, j = TEST_EMPLOYEES.length; i < j; i++) {
employeeDao.merge(TEST_EMPLOYEES[i]);
}
if (log.isInfoEnabled()) {
log.info("TestDataProvider - [addTestEmployees]: Added test employee data.");
}
} catch (StorageException e) {
log.error("TestDataProvider - [addTestEmployees]: Exception catched: " + e.getMessage());
}
}
protected void addTestData() {
addTestSkills();
addTestEmployees();
}
public void afterPropertiesSet() throws Exception {
addTestData();
}
}
注意真正实现初始化的是 afterPropertiesSet() 方法，当然要起效，还需要设定spring的配置文件，设定该部分配置文件如下：
<? xml version="1.0" encoding="UTF-8" ?>
<! DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd" >
< beans default-autowire ="byName" >
< bean id ="storage" class ="org.apache.struts2.showcase.application.MemoryStorage" singleton ="true" />
< bean id ="testDataProvider" class ="org.apache.struts2.showcase.application.TestDataProvider" singleton ="true" lazy-init ="false" />
< bean id ="skillDao" class ="org.apache.struts2.showcase.dao.SkillDao" />
< bean id ="employeeDao" class ="org.apache.struts2.showcase.dao.EmployeeDao" />
最后在web.xml文件配置spring的监听器就ok了，现在启动web服务器， TestDataProvider 就会为持久类进行相应的数据初始化。
后记：如果大家比较感兴趣，可以使用xml代替map玩玩看