java - 将表单发布到服务器时 SpringMvc java.lang.NullPointerException

Question

我有一个带有用户名字段的表单，当我跳出该字段时，我使用 RESTFUL Web Service 来使对 Controller 中处理程序方法的调用。该方法调用一个 DAO 类来检查数据库中用户名是否存在。

这工作正常，但是当表单发布到服务器时，我调用与在处理程序方法中调用的完全相同的函数，但是当它访问该类时，我得到一个 java.lang.NullPointerException调用DAO对象。因此它甚至不会第二次访问DAO对象。

我在所有进行调用的类中都有围绕调用的异常处理程序。关于这里发生的事情的任何想法为什么我会在第二次调用该函数时得到 java.lang.NullPointerException 。这与 Spring 实例化 有什么关系吗？ >DAO 类使用 Singleton 方法或类似的方法？可以采取什么措施来解决这个问题？

这是第一次使用 Web 服务调用该方法时发生的情况(这应该发生):

13011 [http-8084-2] INFO  com.crimetrack.jdbc.JdbcOfficersDAO  - Inside jdbcOfficersDAO
13031 [http-8084-2] DEBUG org.springframework.jdbc.core.JdbcTemplate  - Executing prepared SQL query
13034 [http-8084-2] DEBUG org.springframework.jdbc.core.JdbcTemplate  - Executing prepared SQL statement [SELECT userName FROM crimetrack.tblofficers WHERE userName = ?]
13071 [http-8084-2] DEBUG org.springframework.jdbc.datasource.DataSourceUtils  - Fetching JDBC Connection from DataSource
13496 [http-8084-2] DEBUG org.springframework.jdbc.core.StatementCreatorUtils  - Setting SQL statement parameter value: column index 1, parameter value [adminz], value class [java.lang.String], SQL type unknown
13534 [http-8084-2] DEBUG org.springframework.jdbc.datasource.DataSourceUtils  - Returning JDBC Connection to DataSource
13537 [http-8084-2] INFO  com.crimetrack.jdbc.JdbcOfficersDAO  - No username was found in exception
13537 [http-8084-2] INFO  com.crimetrack.service.ValidateUserNameManager  - UserName :adminz does NOT exist

第二次当表单为“Post”并且验证方法处理表单并调用 Web 服务将调用的相同方法时:

17199 [http-8084-2] INFO  com.crimetrack.service.OfficerRegistrationValidation  - UserName is not null so going to check if its valid for :adminz
17199 [http-8084-2] INFO  com.crimetrack.service.OfficerRegistrationValidation  - User Name in try.....catch block is adminz
17199 [http-8084-2] INFO  com.crimetrack.service.ValidateUserNameManager  - Inside Do UserNameExist about to validate with username : adminz
17199 [http-8084-2] INFO  com.crimetrack.service.ValidateUserNameManager  - UserName :adminz EXCEPTION OCCURED java.lang.NullPointerException

ValidateUserNameManager.java

public class ValidateUserNameManager implements ValidateUserNameIFace {

    private OfficersDAO officerDao;

    private final Logger logger = Logger.getLogger(getClass());


    public boolean DoesUserNameExist(String userName) throws Exception {

        logger.info("Inside Do UserNameExist about to validate with username : " + userName);

        try{

            if(officerDao.OfficerExist(userName) == true){

                logger.info("UserName :" + userName + " does exist");
                return true;

            }else{
                logger.info("UserName :" + userName + " does NOT exist");
                return false;
            }


        }catch(Exception e){

            logger.info("UserName :" + userName + " EXCEPTION OCCURED " + e.toString());
            return false;
        }       

    }

    /**
     * @return the officerDao
     */
    public OfficersDAO getOfficerDao() {
        return officerDao;
    }

    /**
     * @param officerdao the officerDao to set
     */
    public void setOfficerDao(OfficersDAO officerDao) {
        this.officerDao = officerDao;
    }



}

JdbcOfficersDAO.java

public boolean OfficerExist(String userName){

    String dbUserName;

    try{

        logger.info("Inside jdbcOfficersDAO");


        String sql = "SELECT userName FROM crimetrack.tblofficers WHERE userName = ?";

        try{
            dbUserName = (String)getJdbcTemplate().queryForObject(sql, new Object[]{userName},String.class);
            logger.info("Just Returned from database");

        }catch(Exception e){
            logger.info("No username was found in exception");
            return false;
        }

        if(dbUserName == null){

            logger.info("Database did not find any matching records");
        }

        logger.info("after JdbcTemplate");

        if (dbUserName.equals(userName)) {

            logger.info("User Name Exists");
            return true;

        }else{
            logger.info("User Name Does NOT Exists");
            return false;
        }       

    }catch(Exception e){

        logger.info("Exception Message in JdbcOfficersDAO is "+e.getMessage());
        return false;
    }
}

OfficerRegistrationValidation.java

public class OfficerRegistrationValidation implements Validator{

    private final Logger logger = Logger.getLogger(getClass());

    private ValidateUserNameManager validateUserNameManager;


    public boolean supports(Class<?> clazz) {

        return Officers.class.equals(clazz);
    }


    public void validate(Object target, Errors errors) {

        Officers officer = (Officers) target;

        if (officer.getUserName() == null){

            errors.rejectValue("userName", "userName.required");

        }else{

            String userName = officer.getUserName();                    

            logger.info("UserName is not null so going to check if its valid for :" + userName);
            try {

                logger.info("User Name in try.....catch block is " + userName);

                if (validateUserNameManager.DoesUserNameExist(userName)== true){

                    errors.rejectValue("userName", "userName.exist");
                }
            } catch (Exception e) {
                logger.info("Error Occured When validating UserName");
                errors.rejectValue("userName", "userName.error");
            }

        }

        if(officer.getPassword()== null){
            errors.rejectValue("password", "password.required");
        }

        if(officer.getPassword2()== null){
            errors.rejectValue("password2", "password2.required");
        }


        if(officer.getfName() == null){
            errors.rejectValue("fName","fName.required");
        }

        if(officer.getlName() == null){

            errors.rejectValue("lName", "lName.required");
        }

        if (officer.getoName() == null){
            errors.rejectValue("oName", "oName.required");
        }

        if (officer.getEmailAdd() == null){
            errors.rejectValue("emailAdd", "emailAdd.required");
        }

        if (officer.getDob() == null){
            errors.rejectValue("dob", "dob.required");
        }

        if (officer.getGenderId().equals("A")){
            errors.rejectValue("genderId","genderId.required");
        }


        if(officer.getDivisionNo() == 1){

            errors.rejectValue("divisionNo", "divisionNo.required");
        }

        if(officer.getPositionId() == 1){

            errors.rejectValue("positionId", "positionId.required");
        }

        if (officer.getStartDate() == null){

            errors.rejectValue("startDate","startDate.required");
        }

        if(officer.getEndDate() == null){

            errors.rejectValue("endDate","endDate.required");
        }

        logger.info("The Gender ID is " + officer.getGenderId().toString());

        if(officer.getPhoneNo() == null){

            errors.rejectValue("phoneNo", "phoneNo.required");
        }

    }



    /**
     * @return the validateUserNameManager
     */
    public ValidateUserNameManager getValidateUserNameManager() {
        return validateUserNameManager;
    }


    /**
     * @param validateUserNameManager the validateUserNameManager to set
     */
    public void setValidateUserNameManager(
            ValidateUserNameManager validateUserNameManager) {
        this.validateUserNameManager = validateUserNameManager;
    }



}

使用 Logger.Error("Message", e) 更新错误日志:

39024 [http-8084-2] INFO  com.crimetrack.service.OfficerRegistrationValidation  - UserName is not null so going to check if its valid for :adminz
39025 [http-8084-2] INFO  com.crimetrack.service.OfficerRegistrationValidation  - User Name in try.....catch block is adminz
39025 [http-8084-2] ERROR com.crimetrack.service.OfficerRegistrationValidation  - Message
java.lang.NullPointerException
    at com.crimetrack.service.OfficerRegistrationValidation.validate(OfficerRegistrationValidation.java:47)
    at org.springframework.validation.DataBinder.validate(DataBinder.java:725)
    at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.doBind(HandlerMethodInvoker.java:815)
    at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolveHandlerArguments(HandlerMethodInvoker.java:367)
    at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:171)
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:436)
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:424)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:789)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
    at java.lang.Thread.run(Unknown Source)
39025 [http-8084-2] INFO  com.crimetrack.service.OfficerRegistrationValidation  - Error Occured When validating UserName

已更新

ApplicationContext.xml

<beans>
<!-- __________________________________________________________________________________________________ --> 

    <bean id="officerRegistrationValidation" class="com.crimetrack.service.OfficerRegistrationValidation">
            <property name="validateUserNameManager" ref="validateUserNameManager"/>
    </bean>

    <bean id="validateUserNameManager" class="com.crimetrack.service.ValidateUserNameManager">
            <property name="officerDao" ref="officerDao"/>
    </bean>


    <bean id="officerDao" class="com.crimetrack.jdbc.JdbcOfficersDAO" >
            <property name="dataSource" ref="dataSource" />
    </bean>

<!-- __________________________________________________________________________________________________ --> 


    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
            <property name="driverClassName" value="${jdbc.driverClassName}"/>
            <property name="url" value="${jdbc.url}"/>
            <property name="username" value="${jdbc.username}"/>
            <property name="password" value="${jdbc.password}"/>
    </bean>
<!-- __________________________________________________________________________________________________ -->    

    <bean id="propertyConfigurer" 
          class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations">
            <list>
                <value>classpath:jdbc.properties</value>
            </list>
        </property>
    </bean>
<!-- __________________________________________________________________________________________________ -->    

    <bean id="transactionManager" 
          class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource"/>
    </bean>





  </beans>

Servlet.xml

<beans>
<!-- __________________________________________________________________________________________________ --> 

     <bean name="/hello.htm" class="com.crimetrack.web.CountryListController">
        <property name="countryManager" ref="countryManager"/>
     </bean>

    <bean name="/login.htm" class="com.crimetrack.web.AuthenticationController">
        <property name="authenticationManager" ref="authenticationManager"/>  
    </bean>

    <bean name="/officer_registration.htm" class="com.crimetrack.web.OfficerRegistrationController">
        <property name="divisionManager" ref="divisionManager" />
        <property name="positionManager" ref="positionManager" />
        <property name="genderManager" ref="genderManager"/>
    </bean>

<!-- __________________________________________________________________________________________________ -->    

    <bean name="/validateUserName.htm" class="com.crimetrack.web.OfficerRegistrationController">

        <property name="validateUserNameManager" ref="validateUserNameManager"/>    

    </bean>




<!-- __________________________________________________________________________________________________ -->    

      <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"></property>
        <property name="prefix" value="/WEB-INF/jsp/"></property>
        <property name="suffix" value=".jsp"></property>        
      </bean>



</beans>

Answer 1

我认为您忘记 Autowiring ValidateUserNameManager.java 中的 officerDao 字段

尝试添加@Autowire:

@Autowire
private OfficersDAO officerDao;

更新:

更新堆栈跟踪后，我认为是 OfficeRegistrationValidation.java 中的 validateUserNameManager 字段未 Autowiring 。然而，这取决于OfficerRegistrationValidation.java中第47行的内容