JPA -＞ Specification 封装通用方法，解决代码繁琐的烦恼

第一步：定义sql 连接符枚举和sql 条件枚举

package com.miaomiao.common.enums;

/**
 * @program: miaomiao
 * @description:
 * @author: lzy
 * @create: 2020-11-03 09:56
 */
public enum  SqlConnectEnum {
    /**
     * sql 链接属性 and
     */
    AND,

    /**
     * sql 链接属性 or
     */
    OR;

    SqlConnectEnum() {
    }

    public static SqlConnectEnum fromString(String value) {
        return valueOf(value.toLowerCase());
    }
}

package com.miaomiao.common.enums;

/**
 * @program: miaomiao
 * @description:
 * @author: lzy
 * @create: 2020-10-28 19:31
 */
public enum SqlOperateEnum {
    /**
     * sql 条件属性 =
     */
    EQ,

    /**
     * sql 条件属性 !=
     */
    NE,

    /**
     * sql 条件属性 >
     */
    GT,
    /**
     * sql 条件属性 <
     */
    LT,
    /**
     * sql 条件属性 =
     */
    GE,
    /**
     * sql 条件属性 =
     */
    LE,
    /**
     * sql 条件属性 like
     */
    LIKE,
    /**
     * sql 条件属性 in
     */
    IN,
    /**
     * sql 条件属性 为空
     */
    ISNULL,
    /**
     * sql 条件属性 不为空
     */
    ISNOTNULL;

    SqlOperateEnum() {
    }

    public static SqlOperateEnum fromString(String value) {
        return valueOf(value.toLowerCase());

    }
}

第二步：定义自定查询实体

package com.miaomiao.common.sql;

import com.miaomiao.common.enums.SqlConnectEnum;
import com.miaomiao.common.enums.SqlOperateEnum;

import java.io.Serializable;

/**
 * @program: miaomiao
 * @description:
 * @author: lzy
 * @create: 2020-11-02 17:06
 */
public class SqlFilter implements Serializable {
    private static final long serialVersionUID = 1L;
    private String property;
    private Object value;
    private SqlConnectEnum sqlConnectEnum;
    private SqlOperateEnum sqlOperateEnum;



    public SqlFilter() {
    }

    public SqlFilter(SqlConnectEnum sqlConnectEnum, String property, SqlOperateEnum sqlOperateEnum, Object value) {
        this.sqlConnectEnum = sqlConnectEnum;
        this.property = property;
        this.sqlOperateEnum = sqlOperateEnum;
        this.value = value;

    }

    public static SqlFilter andEq(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.AND, property, SqlOperateEnum.EQ, value);
    }
    public static SqlFilter orEq(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.OR, property, SqlOperateEnum.EQ, value);
    }

    public static SqlFilter andNe(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.AND, property, SqlOperateEnum.NE, value);
    }
    public static SqlFilter orNe(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.OR, property, SqlOperateEnum.NE, value);
    }

    public static SqlFilter andGt(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.AND, property, SqlOperateEnum.GT, value);
    }
    public static SqlFilter orGt(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.OR, property, SqlOperateEnum.GT, value);
    }

    public static SqlFilter andLt(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.AND, property, SqlOperateEnum.LT, value);
    }
    public static SqlFilter orLt(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.OR, property, SqlOperateEnum.LT, value);
    }

    public static SqlFilter andGe(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.AND, property, SqlOperateEnum.GE, value);
    }
    public static SqlFilter orGe(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.OR, property, SqlOperateEnum.GE, value);
    }

    public static SqlFilter andLe(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.AND, property, SqlOperateEnum.LE, value);
    }
    public static SqlFilter orLe(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.OR, property, SqlOperateEnum.LE, value);
    }

    public static SqlFilter andLike(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.AND, property, SqlOperateEnum.LIKE, value);
    }
    public static SqlFilter orLike(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.OR, property, SqlOperateEnum.LIKE, value);
    }

    public static SqlFilter andIn(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.AND, property, SqlOperateEnum.IN, value);
    }
    public static SqlFilter orIn(String property, Object value) {
        return new SqlFilter(SqlConnectEnum.OR, property, SqlOperateEnum.IN, value);
    }

    public static SqlFilter andIsNull(String property) {
        return new SqlFilter(SqlConnectEnum.AND, property, SqlOperateEnum.ISNULL, (Object)null);
    }
    public static SqlFilter orIsNull(String property) {
        return new SqlFilter(SqlConnectEnum.OR, property, SqlOperateEnum.ISNULL, (Object)null);
    }

    public static SqlFilter andIsNotNull(String property) {
        return new SqlFilter(SqlConnectEnum.OR, property, SqlOperateEnum.ISNOTNULL, (Object)null);
    }
    public static SqlFilter orIsNotNull(String property) {
        return new SqlFilter(SqlConnectEnum.OR, property, SqlOperateEnum.ISNOTNULL, (Object)null);
    }

    public String getProperty() {
        return property;
    }

    public void setProperty(String property) {
        this.property = property;
    }

    public Object getValue() {
        return value;
    }

    public void setValue(Object value) {
        this.value = value;
    }

    public SqlConnectEnum getSqlConnectEnum() {
        return sqlConnectEnum;
    }

    public void setSqlConnectEnum(SqlConnectEnum sqlConnectEnum) {
        this.sqlConnectEnum = sqlConnectEnum;
    }

    public SqlOperateEnum getSqlOperateEnum() {
        return sqlOperateEnum;
    }

    public void setSqlOperateEnum(SqlOperateEnum sqlOperateEnum) {
        this.sqlOperateEnum = sqlOperateEnum;
    }
}

第三步：在基础实体对象通过继承sqlHelp类转成specification对象方法

package com.miaomiao.common.model;

/**
 * BasePO
 *
 * @author lzy
 */

public class BasePo extends SqlHelp {
    /**
     * 获取按实体参数进行查询的specification
     * @Param 无
     * return specification
     */
    public Specification toSpecification() {
        return getSpecification(this);
    }

    /**
     * 获取按过滤参数和实体参数进行查询的specification
     * @Param sqlFilter
     * return specification
     */
    public Specification toSpecification(SqlFilter sqlFilter) {
        List list = Arrays.asList(sqlFilter);
        return toSpecification(list);
    }

    /**
     * 获取按过滤参数进行查询的specification
     * @Param sqlFilters
     * return specification
     */
    public Specification toSpecification(List sqlFilters) {
        return getSpecificationBySqlFilter(this, sqlFilters);
    }
}

第四步：编写SqlHelp解析类

package com.miaomiao.common.sql;

import com.miaomiao.common.enums.SqlConnectEnum;
import com.miaomiao.common.model.BasePo;
import com.miaomiao.common.utils.SqlUtils;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.util.CollectionUtils;

import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.Path;
import javax.persistence.criteria.Predicate;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;

/**
 * @program: miaomiao
 * @description:
 * @author: lzy
 * @create: 2020-11-04 11:18
 */
public class SqlHelp {
    /**
     * 根据sqlFilters封装Specification
     * @Param basePo 基础实体类
     * @Param sqlFilters 过滤条件集合
     * return 处理结果
     */
    public Specification getSpecificationBySqlFilter(BasePo basePo, List sqlFilters) {
        // sqlFilters为空，执行无过滤查询
        if (CollectionUtils.isEmpty(sqlFilters)){
            return getSpecification(basePo);
        }
        return (Specification) (root, criteriaQuery, criteriaBuilder) -> {
            // 获取所有类属性
            List fields = SqlUtils.getAllField(basePo.getClass());
            // 定义and或者or数组
            List andList = new ArrayList();
            List orList = new ArrayList();
            // 过滤掉自定义参数字段
            List filterFields = SqlUtils.getFilterField(fields, sqlFilters);
            // 循环实体类属性字段查询
            for (Field field : filterFields) {
                try {
                    field.setAccessible(true);
                    Path