[英]Spring-Boot java.lang.NullPointerException: null at javax.el.CompositeELResolver.add(CompositeELResolver…<c:forEach, Validation
我正在嘗試構建一個基本的 Spring-Boot 應用程序。 我在 Controller 中使用 javax.validation。 它將 EL 標記識別為 <c:out value="X" />，但是當視圖具有 <c:forEach items="${collection}... 它會拋出：
java.lang.NullPointerException: null at javax.el.CompositeELResolver.add(CompositeELResolver..
我不知道這是否可能是依賴沖突：（這是我的 pom，我已將所有 servlet 依賴項標記為“已提供”，但它不起作用）
<dependencies>
<!-- spring starters -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-validation</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-security</artifactId>
</dependency>
<dependency>
<groupId>org.apache.tomcat.embed</groupId>
<artifactId>tomcat-embed-jasper</artifactId>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>javax.servlet.jsp-api</artifactId>
<version>2.3.3</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.el</groupId>
<artifactId>javax.el-api</artifactId>
<version>3.0.0</version>
<scope>provided</scope>
</dependency>
<!-- dependency>
<groupId>org.glassfish.web</groupId>
<artifactId>el-impl</artifactId>
<version>2.2</version>
<scope>provided</scope>
</dependency-->
<dependency>
<groupId>javax.servlet.jsp.jstl</groupId>
<artifactId>javax.servlet.jsp.jstl-api</artifactId>
<version>1.2.2</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>jstl</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<!-- jpa persistence -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<!-- bootstrap and dojo -->
<dependency>
<groupId>org.webjars</groupId>
<artifactId>bootstrap</artifactId>
<version>3.3.6</version>
</dependency>
<dependency>
<groupId>org.webjars</groupId>
<artifactId>bootstrap-datepicker</artifactId>
<version>1.0.1</version>
</dependency>
<dependency>
<groupId>org.webjars</groupId>
<artifactId>dojo</artifactId>
<version>1.10.1</version>
</dependency>
<dependency>
<groupId>org.webjars</groupId>
<artifactId>webjars-locator</artifactId>
<version>0.34</version>
</dependency>
<!-- <dependency>
<groupId>org.thymeleaf</groupId>
<artifactId>thymeleaf-spring5</artifactId>
<version>${thymeleaf-version}</version>
</dependency>
<dependency>
<groupId>org.thymeleaf</groupId>
<artifactId>thymeleaf</artifactId>
<version>${thymeleaf-version}</version>
</dependency> -->
<!-- Json -->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>${jackson.version}</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
<version>${jackson.version}</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>${jackson.version}</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-jsr310</artifactId>
<version>${jackson.version}</version>
<scope>compile</scope>
</dependency>
<!-- validation -->
<!--
<dependency>
<groupId>javax.validation</groupId>
<artifactId>validation-api</artifactId>
<version>1.0.0.GA</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator</artifactId>
</dependency>
-->
<!-- spring framework -->
<!-- dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-oxm</artifactId>
<scope>compile</scope>
</dependency-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<!-- excel documents -->
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi</artifactId>
<version>3.15</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi-ooxml</artifactId>
<version>3.15</version>
<scope>compile</scope>
</dependency>
<!-- math library -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-math3</artifactId>
<version>3.6</version>
<scope>compile</scope>
</dependency>
</dependencies>
或者驗證問題：（這是控制器的一部分）
import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.ValidatorFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.BindingResult;
import org.springframework.validation.FieldError;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.SessionAttributes;
import org.springframework.web.bind.support.SessionStatus;
import com.dev.spring.model.tutorial1.EmployeeVO;
import com.dev.spring.service.tutorial1.EmployeeManager;
@Controller
@RequestMapping("/the-good-rest/employee-module")
@SessionAttributes("employee")
public class EmployeeController {
@Autowired
EmployeeManager manager;
String basePath = "tutorial1/";
private Validator validator;
public EmployeeController()
{
ValidatorFactory validatorFactory = Validation.buildDefaultValidatorFactory();
validator = validatorFactory.getValidator();
}
@RequestMapping(value = "/getAllEmployees", method = RequestMethod.GET)
public String getAllEmployees(Model model)
{
model.addAttribute("employees", manager.getAllEmployees());
return basePath + "employeesListDisplay";
}
這是 jsp：
<%@ page contentType="text/html;charset=UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>
<%@ taglib prefix="spring" uri="http://www.springframework.org/tags" %>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<%--@elvariable id="employees" type="com.dev.spring.model.EmployeeVO"--%>
<html>
<head>
<title>Spring MVC Hello World</title>
</head>
<body>
<h2>All Employees in System</h2>
<table border="1">
<tr>
<th>Employee Id</th>
<th>First Name</th>
<th>Last Name</th>
</tr>
<c:forEach items="${employees}" var="employee">
<tr>
<td>${employee.id}</td>
<td>${employee.firstName}</td>
<td>${employee.lastName}</td>
</tr>
</c:forEach>
</table>
</body>
</html>
我發現使應用程序工作的唯一方法。 是將 spring-boot 配置為 spring-mvc 應用程序。
我在 POM 中進行了更改：（已添加）
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<scope>provided</scope>
<!--The rest of dependencies passed from provided to compile-->
在 SpringApplication 中更改了一些 TomcatConfigurationBean（刪除）
部署在 Tomcat 8.1 中，所有 <c:Tags 工作正常，無需更改
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