所以我使用Spring生成随机故事，我在控制器的第73行得到一个NullPointerException，我调用ApplicationContext在获取bean的函数中创建BeanFactory（MadLib和PartOfSpeech类） ）来自文本文件。在添加该函数之前，上下文工作正常。怎么了？
编辑：我知道NullPointerException是什么。我不知道为什么会发生这种情况。此外，它在我注释掉构造函数时有效。我认为问题可能是我试图在它存在之前调用上下文？
编辑2：我尝试将对getBeansFromFiles（）的调用移动到第一个GetMapping（链接）。这消除了NullPointerException，可能是因为Controller bean已经初始化，因此存在上下文。但是当MadLibs被添加到列表中时，bean没有被创建或者至少没有自动装配。有没有一个地方可以把这个电话放在哪里都可以工作？我是否需要实现一个能够在合适的时间进行此调用的界面？
package controllers;
import...
@Controller
@RequestMapping(value = "/madLib")
public class MadLibController {
@Autowired
ApplicationContext context;
public MadLibController(){
getBeansFromFiles();
}
public PartOfSpeech pos(String path){
String input;
try {
input = utility.Util.readFile(path);
} catch (IOException e) {
e.printStackTrace();
input = "v";
}
return new PartOfSpeech(input);
}
public MadLib ml(String path){
String input;
System.out.println(new File("").getAbsolutePath());
try {
input = utility.Util.readFile(path);
} catch (IOException e) {
e.printStackTrace();
input = "v#V#v";
}
return new MadLib(input);
}
public void getBeansFromFiles() {
AutowireCapableBeanFactory beanFactory = context.getAutowireCapableBeanFactory();
File folder = new File("../../txt/ml");
File[] listOfFiles = folder.listFiles();
for (File file : listOfFiles){
System.out.println("File path: " + file.getPath());
MadLib ml = ml(file.getPath());
String beanName = ml.getId();
beanFactory.autowireBean(ml);
beanFactory.initializeBean(ml, beanName);
((MadLibList)context.getBean("madLibList")).getList().add(ml);
}
folder = new File("../../txt/pos");
listOfFiles = folder.listFiles();
for (File file : listOfFiles){
System.out.println("File path: " + file.getPath());
PartOfSpeech pos = pos(file.getPath());
String beanName = pos.getId();
beanFactory.autowireBean(pos);
beanFactory.initializeBean(pos, beanName);
}
}
/*@Bean("verb")
public PartOfSpeech verb(){
return pos("verb");
}
@Bean("hansel2")
public MadLib hansel2(){
return ml("hansel");
}
@Bean("lunch")
public MadLib lunch(){
return ml("lunch");
}*/
@GetMapping
public String links(Model model){
MadLibList list = (MadLibList)context.getBean("madLibList");
//list.getList().add(hansel2());
//list.getList().add(lunch());
model.addAttribute("madLibList", list);
return "madLibLinks";
}
@GetMapping("/{name}")
public String prompts(HttpServletRequest req, HttpServletResponse res,
Model model, @PathVariable("name") String name,
@RequestParam(value = "random", defaultValue = "false") String random){
MadLib madLib = (MadLib)context.getBean(name);
madLib.setAnswers(new ArrayList<String>(madLib.getPrompts().size()));
System.out.println("Answers: " + madLib.getAnswers());
if (random.equals("true")){
System.out.println("Prompts: " + madLib.getPrompts());
for (int i=0; i<madLib.getPrompts().size(); i++){
try {
String posBean = utility.Util.camelCase(madLib.getPrompts().get(i));
PartOfSpeech pos = (PartOfSpeech)context.getBean(posBean);
String word = pos.getWord();
System.out.println(word);
madLib.getAnswers().add(word);
} catch (Exception e) {
System.out.println("exception in randomizing answers for " + madLib.getPrompts().get(i));
System.out.println(e);
madLib.getAnswers().add("");
}
}
}
model.addAttribute("default", "");
model.addAttribute("madLib", madLib);
return "madLibPrompts";
}
@PostMapping(value = "/result")
public String result(Model model, @ModelAttribute("madLib") MadLib madLib, BindingResult result){
System.out.println(madLib.getAnswers().get(0));
//model.addAttribute(madLib);
return "madLibResult";
}
}
答案 0 :(得分：0)
实现BeanDefinitionRegistryPostProcessor并使用beanFactory而不是context
package controllers;
import...
@Controller
@RequestMapping(value = "/madLib")
public class MadLibController implements BeanDefinitionRegistryPostProcessor {
@Autowired
ApplicationContext context;
ConfigurableListableBeanFactory beanFactory;
private BeanDefinitionRegistry registry;
public PartOfSpeech pos(String path){
String input;
try {
input = utility.Util.readFile(path);
} catch (IOException e) {
e.printStackTrace();
input = "v";
}
return new PartOfSpeech(input);
}
public MadLib ml(String path){
String input;
System.out.println(new File("").getAbsolutePath());
try {
input = utility.Util.readFile(path);
} catch (IOException e) {
e.printStackTrace();
input = "v#V#v";
}
return new MadLib(input);
}
public void getBeansFromFiles() {
File folder = new File("../../txt/ml");
File[] listOfFiles = folder.listFiles();
for (File file : listOfFiles){
System.out.println("File path: " + file.getPath());
MadLib ml = ml(file.getPath());
String beanName = ml.getId();
beanFactory.registerSingleton(beanName, ml);
((MadLib)beanFactory.getBean(beanName)).setId(ml.getId());
((MadLib)beanFactory.getBean(beanName)).setTitle(ml.getTitle());
((MadLib)beanFactory.getBean(beanName)).setAnswers(ml.getAnswers());
((MadLib)beanFactory.getBean(beanName)).setPrompts(ml.getPrompts());
((MadLib)beanFactory.getBean(beanName)).setStrings(ml.getStrings());
((MadLibList)beanFactory.getBean("madLibList")).getList().add(ml);
}
folder = new File("../../txt/pos");
listOfFiles = folder.listFiles();
for (File file : listOfFiles){
System.out.println("File path: " + file.getPath());
PartOfSpeech pos = pos(file.getPath());
String beanName = pos.getId();
beanFactory.registerSingleton(beanName, pos);
((PartOfSpeech)beanFactory.getBean(beanName)).setName(pos.getName());
((PartOfSpeech)beanFactory.getBean(beanName)).setWords(pos.getWords());
}
}
@GetMapping
public String links(Model model){
MadLibList list = (MadLibList)beanFactory.getBean("madLibList");
model.addAttribute("madLibList", list);
return "madLibLinks";
}
@GetMapping("/{name}")
public String prompts(HttpServletRequest req, HttpServletResponse res,
Model model, @PathVariable("name") String name,
@RequestParam(value = "random", defaultValue = "false") String random){
MadLib madLib = (MadLib)beanFactory.getBean(name);
//System.out.println(madLib);
madLib.setAnswers(new ArrayList<String>(madLib.getPrompts().size()));
System.out.println("Answers: " + madLib.getAnswers());
if (random.equals("true")){
System.out.println("Prompts: " + madLib.getPrompts());
for (int i=0; i<madLib.getPrompts().size(); i++){
try {
String posBean = utility.Util.camelCase(madLib.getPrompts().get(i));
PartOfSpeech pos = (PartOfSpeech)beanFactory.getBean(posBean);
String word = pos.getWord();
System.out.println(word);
madLib.getAnswers().add(word);
} catch (Exception e) {
System.out.println("exception in randomizing answers for " + madLib.getPrompts().get(i));
System.out.println(e);
e.printStackTrace();
madLib.getAnswers().add("");
}
}
}
model.addAttribute("default", "");
model.addAttribute("madLib", madLib);
return "madLibPrompts";
}
@PostMapping(value = "/result")
public String result(Model model, @ModelAttribute("madLib") MadLib madLib, BindingResult result){
System.out.println(madLib.getAnswers().get(0));
//model.addAttribute(madLib);
return "madLibResult";
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory arg0) throws BeansException {
this.beanFactory = arg0;
getBeansFromFiles();
}
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry arg0) throws BeansException {
this.registry = arg0;
}
}