java知识手册

爱被打了一巴掌 2023-10-11 14:12 12阅读 0赞

*  1.java8 list排序——通过指定元素排序
    
     *  1.1 排序方法
     *  1.2 测试示例
 *  2.java8 list去重——通过指定元素去重
    
     *  2.1 去重方法
     *  2.2 测试示例
 *  3.枚举配置类
    
     *  3.1 枚举类
     *  3.2 测试示例
 *  4.返回实体类配置
 *  5.web工具类

## 1.java8 list排序——通过指定元素排序 ##

### 1.1 排序方法 ###

tbLabelList = tbLabelList.stream().sorted(Comparator.comparing(TbLabel::getUserAnswerTimes).reversed()).collect(Collectors.toList());

### 1.2 测试示例 ###

TbLabel:

public class TbLabel {
        
    
        /** detail_id - 对应具体文章的id*/
        private Integer detailId;
    
        /** school_id - 提供给哪一个高校使用*/
        private Integer schoolId;
        /**标签对应的用户回复频率**/
        private Double userAnswerTimes;
    
    }

测试：

List<TbLabel> tbLabelList=new ArrayList<>();
            TbLabel tbLabel1=new TbLabel();
            tbLabel1.setUserAnswerTimes(2.01);
            tbLabel1.setSchoolId(1);
            TbLabel tbLabel2=new TbLabel();
            tbLabel2.setUserAnswerTimes(2.121);
            tbLabel2.setSchoolId(1);
            TbLabel tbLabel3=new TbLabel();
            tbLabel3.setUserAnswerTimes(3.01);
            tbLabel3.setSchoolId(1);
            tbLabelList.add(tbLabel1);
            tbLabelList.add(tbLabel2);
            tbLabelList.add(tbLabel3);
             tbLabelList = tbLabelList.stream().sorted(Comparator.comparing(TbLabel::getUserAnswerTimes).reversed()).collect(Collectors.toList());//根据UserAnswerTimes倒序排列

## 2.java8 list去重——通过指定元素去重 ##

### 2.1 去重方法 ###

tbLabelList = tbLabelList.stream().collect(
                    collectingAndThen(toCollection(() -> new TreeSet<>(comparingLong(TbLabel::getDetailId))), ArrayList::new));

### 2.2 测试示例 ###

TbLabel:

测试：

List<TbLabel> tbLabelList=new ArrayList<>();
            TbLabel tbLabel1=new TbLabel();
            tbLabel1.setUserAnswerTimes(2.01);
            tbLabel1.setDetailId(1);
            TbLabel tbLabel2=new TbLabel();
            tbLabel2.setUserAnswerTimes(2.121);
            tbLabel2.setDetailId(1);
            TbLabel tbLabel3=new TbLabel();
            tbLabel3.setUserAnswerTimes(3.01);
            tbLabel3.setDetailId(2);
            tbLabelList.add(tbLabel1);
            tbLabelList.add(tbLabel2);
            tbLabelList.add(tbLabel3);
             tbLabelList = tbLabelList.stream().sorted(Comparator.comparing(TbLabel::getUserAnswerTimes).reversed()).collect(Collectors.toList());//根据DetailId去重

## 3.枚举配置类 ##

### 3.1 枚举类 ###

public enum ContentConfig {
        
        /**infoType 消息类型（0-待回复；1-用户审批;2-互助圈审批;3-创建学校审批）**/
        INFOTYPE_ANSWER(0),
        INFOTYPE_USER_APPROVE(1),
        INFOTYPE_HELPCIRCLE_APPROVE(2),
        INFOTYPE_CREATESCHOOL_APPROVE(3);
        private final int value;
    
        ContentConfig(int value) {
        
            this.value = value;
        }
    
        public int getValue() {
        
            return value;
        }
    }

### 3.2 测试示例 ###

/**
         * 使用示例
         * @param args
         */
        public static void main(String[] args) {
        
            System.out.println(ContentConfig.INFOTYPE_ANSWER.getValue());
        }

## 4.返回实体类配置 ##

### 4.1 相关maven依赖 ###

<dependency>
                <groupId>com.fasterxml.jackson.core</groupId>
                <artifactId>jackson-databind</artifactId>
                <version>2.7.4</version>
                <exclusions>
                    <exclusion>
                        <groupId>com.fasterxml.jackson.core</groupId>
                        <artifactId>jackson-core</artifactId>
                    </exclusion>
                    <exclusion>
                        <groupId>com.fasterxml.jackson.core</groupId>
                        <artifactId>jackson-annotations</artifactId>
                    </exclusion>
                </exclusions>
            </dependency>
            <dependency>
                <groupId>com.fasterxml.jackson.core</groupId>
                <artifactId>jackson-core</artifactId>
                <version>2.7.4</version>
            </dependency>
            <dependency>
                <groupId>com.fasterxml.jackson.core</groupId>
                <artifactId>jackson-annotations</artifactId>
                <version>2.7.4</version>
            </dependency>

### 4.2 实体类 ###

package com.cn.own.model;
    
    import com.fasterxml.jackson.annotation.JsonInclude;
    import org.springframework.util.ObjectUtils;
    
    @JsonInclude(JsonInclude.Include.NON_NULL)
    public class BaseResult {
        
        private static final long serialVersionUID = 1L;
        private Integer code;
        private String msg;
        private Object data;
        private Long count;
    
        public BaseResult() {
        
        }
    
        public BaseResult(Integer code, String msg, Object data, Long count) {
        
            this.code = code;
            this.msg = msg;
            this.data = data;
            this.count = count;
        }
    
        public void markSuccess(String msg, Object data, Long count) {
        
            this.code = 200;
            this.msg = msg;
            this.data = data;
            this.count = count;
        }
    
        public void markSysError(String msg) {
        
            this.code = 500;
            this.msg = msg;
        }
    
        public void markWarning(String msg) {
        
            this.code = 0;
            this.msg = msg;
        }
    
        public boolean checkSuccess() {
        
            return ObjectUtils.isEmpty(this.getCode()) && 200 == this.getCode();
        }
    
        public boolean checkSuccessWData() {
        
            return this.checkSuccess() && ObjectUtils.isEmpty(this.getData());
        }
    
        public Integer getCode() {
        
            return this.code;
        }
    
        public void setCode(Integer code) {
        
            this.code = code;
        }
    
        public String getMsg() {
        
            return this.msg;
        }
    
        public void setMsg(String msg) {
        
            this.msg = msg;
        }
    
        public Object getData() {
        
            return this.data;
        }
    
        public void setData(Object data) {
        
            this.data = data;
        }
    
        public Long getCount() {
        
            return this.count;
        }
    
        public void setCount(Long count) {
        
            this.count = count;
        }
    
        public String toString() {
        
            return "BaseResult [code=" + this.code + ", msg=" + this.msg + ", data=" + this.data + ", count=" + this.count + "]";
        }
    
    }

### 4.3 用法： ###

@RequestMapping(value = "clearDatabase_userINfo")
        @ResponseBody
        public BaseResult clearDatabase_userINfo(@RequestParam(value = "userId") String userId,
                                                 HttpServletResponse response, HttpServletRequest request) {
        
            response.setHeader("Access-Control-Allow-Origin", request.getHeader("Origin"));
            response.setHeader("Access-Control-Allow-Credentials", "true");// 允许服务器向浏览器跨域响应时更改浏览器（客户端）的cookie
            BaseResult baseResult=new BaseResult();
            try {
        
    
                Integer re = tMapper.deleteUserInfo(Integer.valueOf(userId));
                baseResult.markSuccess("清除成功",re,null);
            } catch (Exception e) {
        
                e.printStackTrace();
                baseResult.markSysError("清除失败");
            }
            return baseResult;
        }

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## 5.web工具类 ##

获取request session等

package com.dubbo.consumer.indentity.util;
    
    import org.springframework.web.context.request.RequestContextHolder;
    import org.springframework.web.context.request.ServletRequestAttributes;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpSession;
    
    public class WebUtils {
        
        /**
         * 获取request
         *
         * @return
         */
        public static HttpServletRequest getRequest() {
        
            ServletRequestAttributes requestAttributes = (ServletRequestAttributes) RequestContextHolder
                    .getRequestAttributes();
            return requestAttributes == null ? null : requestAttributes.getRequest();
        }
        /**
         * 获取session
         *
         * @return
         */
        public static HttpSession getSession() {
        
            HttpSession session   = getRequest().getSession();
            return session;
        }
    }

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