背景

REST的概念這里不多過多闡述。在REST中，資源通過URL進行識別和定位。一般來說，以下這些HTTP方法通常會匹配為如下的CRUD動作：

Create：POST

Read：GET

Update：PUT或PATCH

Delete：DELETE

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@ResponseBody：此注解會告知Spring，我們要將返回的對象作為資源發送給客戶端，并將其轉化為客戶端可接受的表現形式。如果客戶端的Accept頭部信息表明它接受"application/json"，并且jackson JSON庫位于應用程序的路徑下，那么會將返回結果列表轉化為json格式。

@RestController：此注解能為控制器的所有處理方法應用消息轉化功能。不必為每個方法都添加@ResponseBody了。

@ResponseEntity：作為@ResponseBody的替代方案，@ResponseEntity中可以包含響應相關的元數據（如頭部信息和狀態碼）以及要轉換成資源表述的對象。

@ResponseStatus：此注解可以指定狀態碼。

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環境搭建相關

SpringMVC相關的jar包全部引入便是

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c3p0相關jar包：

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jackson相關jar包：

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oracle jdbc 相關jar包：

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spring.xml 文件代碼如下圖所示：

<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:context="http://www.springframework.org/schema/context"xmlns:mvc="http://www.springframework.org/schema/mvc"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsdhttp://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd"> <!-- 定義要掃描 controller的包 --><context:component-scan base-package="cn.com.restapi.controller" /><context:component-scan base-package="cn.com.restapi.daoimpl"/><context:component-scan base-package="cn.com.restapi.serviceimpl"/><mvc:default-servlet-handler /> <!-- 啟動注解驅動 SpringMVC 功能 --><mvc:annotation-driven /><!-- 引用配置文件 --><context:property-placeholder location="classpath:jdbc.properties"/><!-- 配置視圖解析器解析路徑 --><bean class="org.springframework.web.servlet.view.InternalResourceViewResolver" id="internalResourceViewResolver"><!-- 定義視圖存放路徑 --><property name="prefix" value="/WEB-INF/jsp/" /><!-- 定義視圖后綴 --><property name="suffix" value=".jsp" /></bean><!-- 1、聲明數據源對象：C3P0連接池 --><bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"><!-- 加載jdbc驅動 --><property name="driverClass" value="${driverClass}"></property><!-- jdbc連接地址 --><property name="jdbcUrl" value="${jdbcUrl}"></property><!-- 連接數據庫的用戶名 --><property name="user" value="${user}"></property><!-- 連接數據庫的密碼 --><property name="password" value="${password}"></property><!-- 數據庫的初始化連接數 --><property name="initialPoolSize" value="3"></property><!-- 數據庫的最大連接數 --><property name="maxPoolSize" value="10"></property><!-- 數據庫最多執行的事務 --><property name="maxStatements" value="100"></property><!-- 連接數量不夠時每次的增量 --><property name="acquireIncrement" value="2"></property> </bean><!-- 創建jdbcTemplate對象 --><bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate"><property name="dataSource" ref="dataSource"></property></bean></beans>

?jdbc.properties 配置文件如下圖所示：

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整個項目的目錄如下圖所示：

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實體類Employee.java代碼：

package cn.com.restapi.model;public class Employee {private int employeeID;private String employeeName;private int age;private String address;private String sex;@Overridepublic String toString(){return "Employee[EMPLOYEE_ID=" + employeeID + ",EMPLOYEENAME=" + employeeName + ",AGE=" + age + ",ADDRESS=" + address + ",SEX=" + sex + "]";}//get and set........ }

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dao層代碼：

import java.util.List; import cn.com.restapi.model.Employee;public interface EmployeeDao {public List<Employee> getEmployees();public Employee getEmployeeByID(int id);public int createEmployee(Employee employee);public int updateEmployee(Employee employee);public int deleteEmployee(Employee employee);public boolean ifEmployeeExist(Employee employee); }

daoimpl層代碼，此處使用c3p0數據源和Spring中的JdbcTemplate模板。

package cn.com.restapi.daoimpl;import java.sql.ResultSet; import java.sql.SQLException; import java.util.List; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.jdbc.core.JdbcTemplate; import org.springframework.jdbc.core.RowMapper; import org.springframework.stereotype.Repository; import cn.com.restapi.dao.EmployeeDao; import cn.com.restapi.model.Employee;@Repository public class EmployeeDaoImpl implements EmployeeDao{@Autowiredprivate JdbcTemplate jdbcTemplate;private Log log = LogFactory.getLog(EmployeeDaoImpl.class.getName());@Overridepublic List<Employee> getEmployees() {// TODO Auto-generated method stubString sql = "SELECT EMPLOYEE_ID,EMPLOYEE_NAME,AGE,ADDRESS,SEX FROM EMPLOYEE";log.info(sql);return jdbcTemplate.query(sql, new EmployeeRowMapper());}@Overridepublic Employee getEmployeeByID(int id) {// TODO Auto-generated method stubString sql = "SELECT EMPLOYEE_ID,EMPLOYEE_NAME,AGE,ADDRESS,SEX FROM EMPLOYEE WHERE EMPLOYEE_ID = ?";log.info(sql);List<Employee> employees = this.jdbcTemplate.query(sql, new EmployeeRowMapper(),id);if (employees.isEmpty()) {return null;}return employees.get(0);}@Overridepublic int createEmployee(Employee employee) {// TODO Auto-generated method stubString sql = "INSERT INTO EMPLOYEE(EMPLOYEE_ID,EMPLOYEE_NAME,AGE,ADDRESS,SEX) VALUE(?,?,?,?,?)";log.info(sql);int rowNum = this.jdbcTemplate.update(sql,employee.getEmployeeID(),employee.getEmployeeName(),employee.getAge(),employee.getAddress(),employee.getSex());return rowNum;}@Overridepublic int updateEmployee(Employee employee) {// TODO Auto-generated method stubString sql = "UPDATE EMPLOYEE SET EMPLOYEE_NAME = ?,AGE = ?,ADDRESS = ?,SEX = ? WHERE EMPLOYEE_ID = ?";log.info(sql);int rowNum = this.jdbcTemplate.update(sql,employee.getEmployeeName(),employee.getAge(),employee.getAddress(),employee.getSex(),employee.getEmployeeID());return rowNum;}@Overridepublic int deleteEmployee(Employee employee) {// TODO Auto-generated method stubString sql = "DELETE EMPLOYEE WHERE EMPLOYEE_ID = ?";log.info(sql);int rowNum = this.jdbcTemplate.update(sql,employee.getEmployeeID());return rowNum;}public class EmployeeRowMapper implements RowMapper<Employee>{@Overridepublic Employee mapRow(ResultSet rSet, int rowNum) throws SQLException {// TODO Auto-generated method stubEmployee employee = new Employee();employee.setEmployeeID(rSet.getInt("EMPLOYEE_ID"));employee.setEmployeeName(rSet.getString("EMPLOYEE_NAME"));employee.setAddress(rSet.getString("ADDRESS"));employee.setAge(rSet.getInt("AGE"));employee.setSex(rSet.getString("SEX"));return employee;}}@Overridepublic boolean ifEmployeeExist(Employee employee) {// TODO Auto-generated method stubEmployee employee2 = this.getEmployeeByID(employee.getEmployeeID());if (employee2 == null) {return true;}return false;}}

Service層代碼：

package cn.com.restapi.service;import java.util.List; import cn.com.restapi.model.Employee;public interface EmployeeService {public List<Employee> getEmployees();public Employee getEmployee(int id);public int createEmployee(Employee employee);public int updateEmployee(Employee employee);public int deleteEmployee(Employee employee);public boolean ifEmployeeExist(Employee employee); }

ServiceImpl層代碼：

package cn.com.restapi.serviceimpl;import java.util.List; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; import cn.com.restapi.dao.EmployeeDao; import cn.com.restapi.model.Employee; import cn.com.restapi.service.EmployeeService;@Service public class EmployeeServiceImpl implements EmployeeService{@Autowiredprivate EmployeeDao employeeDao;@Overridepublic List<Employee> getEmployees() {// TODO Auto-generated method stubList<Employee> employees = employeeDao.getEmployees();return employees;}@Overridepublic Employee getEmployee(int id) {// TODO Auto-generated method stubEmployee employee = employeeDao.getEmployeeByID(id);return employee;}@Overridepublic int createEmployee(Employee employee) {// TODO Auto-generated method stubint rowNum = employeeDao.createEmployee(employee);return rowNum;}@Overridepublic int updateEmployee(Employee employee) {// TODO Auto-generated method stubint rowNum = employeeDao.updateEmployee(employee);return rowNum;}@Overridepublic int deleteEmployee(Employee employee) {// TODO Auto-generated method stubint rowNum = employeeDao.deleteEmployee(employee);return rowNum;}@Overridepublic boolean ifEmployeeExist(Employee employee) {// TODO Auto-generated method stubboolean b = employeeDao.ifEmployeeExist(employee);return b;}}

?Controller層代碼，分別對Employee表實現CRUD操作：

package cn.com.restapi.controller;import java.net.URI; import java.util.List; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.http.HttpHeaders; import org.springframework.http.HttpStatus; import org.springframework.http.ResponseEntity; import org.springframework.web.bind.annotation.ExceptionHandler; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RequestBody; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestMethod; import org.springframework.web.bind.annotation.ResponseStatus; import org.springframework.web.bind.annotation.RestController; import org.springframework.web.util.UriComponentsBuilder; import cn.com.restapi.model.Employee; import cn.com.restapi.model.EmployeeNotFoundException; import cn.com.restapi.model.Error; import cn.com.restapi.service.EmployeeService;@RestController public class EmployeeController {@Autowiredpublic EmployeeService employeeService;public Log log = LogFactory.getLog(EmployeeController.class.getName());@RequestMapping(value="/employee",method = RequestMethod.GET)public ResponseEntity<List<Employee>> getEmployees(){log.info("getEmployee method called");List<Employee> employees = employeeService.getEmployees();if (employees.isEmpty()) {return new ResponseEntity<List<Employee>>(employees,HttpStatus.NO_CONTENT);}return new ResponseEntity<List<Employee>>(employees,HttpStatus.OK);}@RequestMapping(value="/employee/{id}",method = RequestMethod.GET)public Employee getEmployeeByID(@PathVariable("id") int id){log.info("getEmployeeByID method called");Employee employee = employeeService.getEmployee(id);if (employee == null) {throw new EmployeeNotFoundException(id);}return employee;}@ExceptionHandler(EmployeeNotFoundException.class)@ResponseStatus(HttpStatus.NOT_FOUND)public ResponseEntity<Error> EmployeeNotFound(EmployeeNotFoundException e){int employeeId = e.getEmployeeId();Error error = new Error(4, "Employee [" + employeeId + "] not found");return new ResponseEntity<Error>(error,HttpStatus.NOT_FOUND);}@RequestMapping(value="/employee",method = RequestMethod.POST,consumes="application/json")public ResponseEntity<?> creatEmployee(@RequestBody Employee employee,UriComponentsBuilder ucb){if (employeeService.ifEmployeeExist(employee)) {Error error = new Error(4, "Employee [id=" + employee.getEmployeeID() + "] already exist");return new ResponseEntity<Error>(error,HttpStatus.CONFLICT);}employeeService.createEmployee(employee);HttpHeaders headers = new HttpHeaders();URI locationUri = ucb.path("/RESTAPI/").path(String.valueOf(employee.getEmployeeID())).build().toUri();headers.setLocation(locationUri);ResponseEntity<Employee> responseEntity = new ResponseEntity<Employee>(employee,headers,HttpStatus.CREATED);return responseEntity;}@RequestMapping(value="/employee",method = RequestMethod.PUT,consumes="application/json")public ResponseEntity<?> updateEmployee(@RequestBody Employee employee,UriComponentsBuilder ucb){if (!employeeService.ifEmployeeExist(employee)) {Error error = new Error(4, "Employee [id=" + employee.getEmployeeID() + "] not found");return new ResponseEntity<Error>(error,HttpStatus.NOT_FOUND);}employeeService.updateEmployee(employee);HttpHeaders headers = new HttpHeaders();URI locationUri = ucb.path("/RESTAPI/").path(String.valueOf(employee.getEmployeeID())).build().toUri();headers.setLocation(locationUri);ResponseEntity<Employee> responseEntity = new ResponseEntity<Employee>(employee,headers,HttpStatus.OK);return responseEntity;}@RequestMapping(value="/employee",method=RequestMethod.DELETE,consumes="application/json")public ResponseEntity<?> deleteEmployee(@RequestBody Employee employee){if (!employeeService.ifEmployeeExist(employee)) {Error error = new Error(4, "Employee [id=" + employee.getEmployeeID() + "] not found");return new ResponseEntity<Error>(error,HttpStatus.NOT_FOUND);}employeeService.deleteEmployee(employee);return new ResponseEntity<Employee>(HttpStatus.NO_CONTENT);}}

?Controller層中有兩個實體類Error，EmployeeNotFoundException。用于返回錯誤信息：

package cn.com.restapi.model;public class Error {private int code;private String message;public Error(int code,String message){this.code = code;this.message = message;}public int getCode(){return code;}public String getMessage(){return message;} } package cn.com.restapi.model;public class EmployeeNotFoundException extends RuntimeException{private int EmployeeId;public EmployeeNotFoundException(int employeeId){this.EmployeeId = employeeId;}public int getEmployeeId(){return EmployeeId;} }

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