Mybatis Generator 运行后,我看到在实体类包中出现了四个类。多出来两个带 Example 的是什么呢?
限于篇幅,只研究 Department.java 和 DepartmentExample.java 这两个就好了,Employee 的估计应该也差不多。
8.1 Department.java
package com.hh.ssm.bean;
import java.util.Date;
public class Department {
private Integer departmentId;
private String departmentName;
private Date gmtCreate;
private Date gmtModified;
public Integer getDepartmentId() {
return departmentId;
}
public void setDepartmentId(Integer departmentId) {
this.departmentId = departmentId;
}
public String getDepartmentName() {
return departmentName;
}
// 看到下面的这个细节,就觉得自己平时不够细致了。
public void setDepartmentName(String departmentName) {
this.departmentName = departmentName == null ? null : departmentName.trim();
}
public Date getGmtCreate() {
return gmtCreate;
}
public void setGmtCreate(Date gmtCreate) {
this.gmtCreate = gmtCreate;
}
public Date getGmtModified() {
return gmtModified;
}
public void setGmtModified(Date gmtModified) {
this.gmtModified = gmtModified;
}
}
从上面的代码可以得出以下几点结论:
1. 成员变量与表中的各个列在名称和数据类型上都能很好的一一对应
2. 而且命名符合小写驼峰规范
3. 无构造函数,如果需要可以自己添加,但一定不能少了无参构造函数
4. 可以尝试重写 toString() 方法
8.2 DepartmentExample.java
这个是 Mybatis Generator 生成的与 Department 实体相关的另一个实体。干嘛用的呢?我研究一下里面的构成,大体上知道了思路所在。这个类的里面有一个内部静态抽象类 GeneratedCriteria ,还有两个内部静态类 Criteria 和 Criterion 。
8.2.1 SQL 拼接函数(叫方法感觉怪怪的,用于拼接 SQL 语句的方法?)
可以看见在不涉及成员变量的方法大概有以下几个:
8.2.2 查询条件拼接函数(拼接查询条件的方法)
针对每个成员变量,Mybatis Generator 都提供了个查询条件的拼接函数。
1. is null
2. not null
3. =
4. <>
5. >
6. >=
7. <
8. <=
9. like
10. not like
11. in
12. not in
13. between
14. not between
package com.hh.ssm.bean;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
public class DepartmentExample {
protected String orderByClause; // order by 子句
protected boolean distinct; // distinct 子句,是否去重复
protected List<Criteria> oredCriteria; // 所有条件的集合,这些条件的关系是 or
// 无参构造函数,创建条件 List
public DepartmentExample() {
oredCriteria = new ArrayList<Criteria>();
}
// getter 和 setter , oredCriteria 的setter就没有了,因为在构造函数中已经写了
public void setOrderByClause(String orderByClause) {
this.orderByClause = orderByClause;
}
public String getOrderByClause() {
return orderByClause;
}
public void setDistinct(boolean distinct) {
this.distinct = distinct;
}
public boolean isDistinct() {
return distinct;
}
public List<Criteria> getOredCriteria() {
return oredCriteria;
}
// or 方法:向条件集合中增加条件
public void or(Criteria criteria) {
oredCriteria.add(criteria);
}
public Criteria or() {
Criteria criteria = createCriteriaInternal();
oredCriteria.add(criteria);
return criteria;
}
public Criteria createCriteria() {
Criteria criteria = createCriteriaInternal();
if (oredCriteria.size() == 0) {
oredCriteria.add(criteria);
}
return criteria;
}
protected Criteria createCriteriaInternal() {
Criteria criteria = new Criteria();
return criteria;
}
public void clear() {
oredCriteria.clear();
orderByClause = null;
distinct = false;
}
protected abstract static class GeneratedCriteria {
protected List<Criterion> criteria;
protected GeneratedCriteria() {
super();
criteria = new ArrayList<Criterion>();
}
public boolean isValid() {
return criteria.size() > 0;
}
public List<Criterion> getAllCriteria() {
return criteria;
}
public List<Criterion> getCriteria() {
return criteria;
}
protected void addCriterion(String condition) {
if (condition == null) {
throw new RuntimeException("Value for condition cannot be null");
}
criteria.add(new Criterion(condition));
}
protected void addCriterion(String condition, Object value, String property) {
if (value == null) {
throw new RuntimeException("Value for " + property + " cannot be null");
}
criteria.add(new Criterion(condition, value));
}
protected void addCriterion(String condition, Object value1, Object value2, String property) {
if (value1 == null || value2 == null) {
throw new RuntimeException("Between values for " + property + " cannot be null");
}
criteria.add(new Criterion(condition, value1, value2));
}
public Criteria andDepartmentIdIsNull() {
addCriterion("department_id is null");
return (Criteria) this;
}
public Criteria andDepartmentIdIsNotNull() {
addCriterion("department_id is not null");
return (Criteria) this;
}
public Criteria andDepartmentIdEqualTo(Integer value) {
addCriterion("department_id =", value, "departmentId");
return (Criteria) this;
}
public Criteria andDepartmentIdNotEqualTo(Integer value) {
addCriterion("department_id <>", value, "departmentId");
return (Criteria) this;
}
public Criteria andDepartmentIdGreaterThan(Integer value) {
addCriterion("department_id >", value, "departmentId");
return (Criteria) this;
}
public Criteria andDepartmentIdGreaterThanOrEqualTo(Integer value) {
addCriterion("department_id >=", value, "departmentId");
return (Criteria) this;
}
public Criteria andDepartmentIdLessThan(Integer value) {
addCriterion("department_id <", value, "departmentId");
return (Criteria) this;
}
public Criteria andDepartmentIdLessThanOrEqualTo(Integer value) {
addCriterion("department_id <=", value, "departmentId");
return (Criteria) this;
}
public Criteria andDepartmentIdIn(List<Integer> values) {
addCriterion("department_id in", values, "departmentId");
return (Criteria) this;
}
public Criteria andDepartmentIdNotIn(List<Integer> values) {
addCriterion("department_id not in", values, "departmentId");
return (Criteria) this;
}
public Criteria andDepartmentIdBetween(Integer value1, Integer value2) {
addCriterion("department_id between", value1, value2, "departmentId");
return (Criteria) this;
}
public Criteria andDepartmentIdNotBetween(Integer value1, Integer value2) {
addCriterion("department_id not between", value1, value2, "departmentId");
return (Criteria) this;
}
public Criteria andDepartmentNameIsNull() {
addCriterion("department_name is null");
return (Criteria) this;
}
public Criteria andDepartmentNameIsNotNull() {
addCriterion("department_name is not null");
return (Criteria) this;
}
public Criteria andDepartmentNameEqualTo(String value) {
addCriterion("department_name =", value, "departmentName");
return (Criteria) this;
}
public Criteria andDepartmentNameNotEqualTo(String value) {
addCriterion("department_name <>", value, "departmentName");
return (Criteria) this;
}
public Criteria andDepartmentNameGreaterThan(String value) {
addCriterion("department_name >", value, "departmentName");
return (Criteria) this;
}
public Criteria andDepartmentNameGreaterThanOrEqualTo(String value) {
addCriterion("department_name >=", value, "departmentName");
return (Criteria) this;
}
public Criteria andDepartmentNameLessThan(String value) {
addCriterion("department_name <", value, "departmentName");
return (Criteria) this;
}
public Criteria andDepartmentNameLessThanOrEqualTo(String value) {
addCriterion("department_name <=", value, "departmentName");
return (Criteria) this;
}
public Criteria andDepartmentNameLike(String value) {
addCriterion("department_name like", value, "departmentName");
return (Criteria) this;
}
public Criteria andDepartmentNameNotLike(String value) {
addCriterion("department_name not like", value, "departmentName");
return (Criteria) this;
}
public Criteria andDepartmentNameIn(List<String> values) {
addCriterion("department_name in", values, "departmentName");
return (Criteria) this;
}
public Criteria andDepartmentNameNotIn(List<String> values) {
addCriterion("department_name not in", values, "departmentName");
return (Criteria) this;
}
public Criteria andDepartmentNameBetween(String value1, String value2) {
addCriterion("department_name between", value1, value2, "departmentName");
return (Criteria) this;
}
public Criteria andDepartmentNameNotBetween(String value1, String value2) {
addCriterion("department_name not between", value1, value2, "departmentName");
return (Criteria) this;
}
public Criteria andGmtCreateIsNull() {
addCriterion("gmt_create is null");
return (Criteria) this;
}
public Criteria andGmtCreateIsNotNull() {
addCriterion("gmt_create is not null");
return (Criteria) this;
}
public Criteria andGmtCreateEqualTo(Date value) {
addCriterion("gmt_create =", value, "gmtCreate");
return (Criteria) this;
}
public Criteria andGmtCreateNotEqualTo(Date value) {
addCriterion("gmt_create <>", value, "gmtCreate");
return (Criteria) this;
}
public Criteria andGmtCreateGreaterThan(Date value) {
addCriterion("gmt_create >", value, "gmtCreate");
return (Criteria) this;
}
public Criteria andGmtCreateGreaterThanOrEqualTo(Date value) {
addCriterion("gmt_create >=", value, "gmtCreate");
return (Criteria) this;
}
public Criteria andGmtCreateLessThan(Date value) {
addCriterion("gmt_create <", value, "gmtCreate");
return (Criteria) this;
}
public Criteria andGmtCreateLessThanOrEqualTo(Date value) {
addCriterion("gmt_create <=", value, "gmtCreate");
return (Criteria) this;
}
public Criteria andGmtCreateIn(List<Date> values) {
addCriterion("gmt_create in", values, "gmtCreate");
return (Criteria) this;
}
public Criteria andGmtCreateNotIn(List<Date> values) {
addCriterion("gmt_create not in", values, "gmtCreate");
return (Criteria) this;
}
public Criteria andGmtCreateBetween(Date value1, Date value2) {
addCriterion("gmt_create between", value1, value2, "gmtCreate");
return (Criteria) this;
}
public Criteria andGmtCreateNotBetween(Date value1, Date value2) {
addCriterion("gmt_create not between", value1, value2, "gmtCreate");
return (Criteria) this;
}
public Criteria andGmtModifiedIsNull() {
addCriterion("gmt_modified is null");
return (Criteria) this;
}
public Criteria andGmtModifiedIsNotNull() {
addCriterion("gmt_modified is not null");
return (Criteria) this;
}
public Criteria andGmtModifiedEqualTo(Date value) {
addCriterion("gmt_modified =", value, "gmtModified");
return (Criteria) this;
}
public Criteria andGmtModifiedNotEqualTo(Date value) {
addCriterion("gmt_modified <>", value, "gmtModified");
return (Criteria) this;
}
public Criteria andGmtModifiedGreaterThan(Date value) {
addCriterion("gmt_modified >", value, "gmtModified");
return (Criteria) this;
}
public Criteria andGmtModifiedGreaterThanOrEqualTo(Date value) {
addCriterion("gmt_modified >=", value, "gmtModified");
return (Criteria) this;
}
public Criteria andGmtModifiedLessThan(Date value) {
addCriterion("gmt_modified <", value, "gmtModified");
return (Criteria) this;
}
public Criteria andGmtModifiedLessThanOrEqualTo(Date value) {
addCriterion("gmt_modified <=", value, "gmtModified");
return (Criteria) this;
}
public Criteria andGmtModifiedIn(List<Date> values) {
addCriterion("gmt_modified in", values, "gmtModified");
return (Criteria) this;
}
public Criteria andGmtModifiedNotIn(List<Date> values) {
addCriterion("gmt_modified not in", values, "gmtModified");
return (Criteria) this;
}
public Criteria andGmtModifiedBetween(Date value1, Date value2) {
addCriterion("gmt_modified between", value1, value2, "gmtModified");
return (Criteria) this;
}
public Criteria andGmtModifiedNotBetween(Date value1, Date value2) {
addCriterion("gmt_modified not between", value1, value2, "gmtModified");
return (Criteria) this;
}
}
public static class Criteria extends GeneratedCriteria {
protected Criteria() {
super();
}
}
public static class Criterion {
private String condition;
private Object value;
private Object secondValue;
private boolean noValue;
private boolean singleValue;
private boolean betweenValue;
private boolean listValue;
private String typeHandler;
public String getCondition() {
return condition;
}
public Object getValue() {
return value;
}
public Object getSecondValue() {
return secondValue;
}
public boolean isNoValue() {
return noValue;
}
public boolean isSingleValue() {
return singleValue;
}
public boolean isBetweenValue() {
return betweenValue;
}
public boolean isListValue() {
return listValue;
}
public String getTypeHandler() {
return typeHandler;
}
protected Criterion(String condition) {
super();
this.condition = condition;
this.typeHandler = null;
this.noValue = true;
}
protected Criterion(String condition, Object value, String typeHandler) {
super();
this.condition = condition;
this.value = value;
this.typeHandler = typeHandler;
if (value instanceof List<?>) {
this.listValue = true;
} else {
this.singleValue = true;
}
}
protected Criterion(String condition, Object value) {
this(condition, value, null);
}
protected Criterion(String condition, Object value, Object secondValue, String typeHandler) {
super();
this.condition = condition;
this.value = value;
this.secondValue = secondValue;
this.typeHandler = typeHandler;
this.betweenValue = true;
}
protected Criterion(String condition, Object value, Object secondValue) {
this(condition, value, secondValue, null);
}
}
}